Add crt library link support, and split crt/nocrt cc_toolchains.

This CL adds support for splitting device cc_toolchains to crt/no_crt
variants, and adding the crtbegin/crtend libraries to shared libraries
link actions.

Sample aquery output for:

libasyncio (crt link enabled): https://gist.github.com/jin/b4c7e364f7a0dd6b429ed0d424df5674

libc (crt link disabled): https://gist.github.com/jin/52eb86114db69cc2e4d3adbb8a60c89d

The no_crt variants are used by very few modules: libc/libdl/libm, and
crt objects themselves.

Test: presubmits

Change-Id: Icb8847bec888d332dcb9d4e92df3863e7d237ca1

1 files changed, 89 insertions, 100 deletions

diff --git a/BUILD.bazel b/BUILD.bazel
index 919f9cab2..11c9d332f 100644
--- a/BUILD.bazel
+++ b/BUILD.bazel
@@ -59,67 +59,6 @@ android_cc_toolchain(
     toolchain_identifier = "x86_64-toolchain",
 )
 
-toolchain(
-    name = "cc_toolchain_x86_64_def",
-    exec_compatible_with = [
-        "//build/bazel/platforms/arch:x86_64",
-        "//build/bazel/platforms/os:linux",
-    ],
-    target_compatible_with = [
-        "//build/bazel/platforms/arch:x86_64",
-        "//build/bazel/platforms/os:android",
-    ],
-    toolchain = ":cc_toolchain_x86_64",
-    toolchain_type = "@bazel_tools//tools/cpp:toolchain_type",
-)
-
-# Toolchain to compile for the linux host.
-# TODO(b/186628704): automatically generate from Soong.
-android_cc_toolchain(
-    name = "cc_toolchain_x86_64_linux_host",
-    target_os = "linux_glibc",
-    target_arch = "x86_64",
-    clang_version = ":clang",
-    clang_version_directory = generated_constants.CLANG_DEFAULT_VERSION,
-    libclang_rt_builtin = _LIBCLANG_RT_PREBUILT_MAP["//build/bazel/platforms/os_arch:linux_glibc_x86_64"],
-    linker_flags = [
-        "-m64",
-        "-Wl,-z,noexecstack",
-        "-Wl,-z,relro",
-        "-Wl,-z,now",
-        "-Wl,--no-undefined-version",
-    ],
-    target_flags = [
-        "-m64",
-        "-fdiagnostics-color",
-        "-Wa,--noexecstack",
-        "-fPIC",
-        "-U_FORTIFY_SOURCE",
-        "-D_FORTIFY_SOURCE=2",
-        "-fstack-protector",
-        # Workaround differences in inttypes.h between host and target.
-        # See bug 12708004.
-        "-D__STDC_FORMAT_MACROS",
-        "-D__STDC_CONSTANT_MACROS",
-    ],
-    toolchain_identifier = "x86_64-toolchain",
-)
-
-# TODO(b/181803350): Fix linux toolchain flag set, as the current flags are for android.
-toolchain(
-    name = "cc_toolchain_x86_64_linux_host_def",
-    exec_compatible_with = [
-        "//build/bazel/platforms/arch:x86_64",
-        "//build/bazel/platforms/os:linux",
-    ],
-    target_compatible_with = [
-        "//build/bazel/platforms/arch:x86_64",
-        "//build/bazel/platforms/os:linux",
-    ],
-    toolchain = ":cc_toolchain_x86_64_linux_host",
-    toolchain_type = "@bazel_tools//tools/cpp:toolchain_type",
-)
-
 # x86 toolchain definition.
 android_cc_toolchain(
     name = "cc_toolchain_x86",
@@ -140,20 +79,6 @@ android_cc_toolchain(
     toolchain_identifier = "x86-toolchain",
 )
 
-toolchain(
-    name = "cc_toolchain_x86_def",
-    exec_compatible_with = [
-        "//build/bazel/platforms/arch:x86_64",
-        "//build/bazel/platforms/os:linux",
-    ],
-    target_compatible_with = [
-        "//build/bazel/platforms/arch:x86",
-        "//build/bazel/platforms/os:android",
-    ],
-    toolchain = ":cc_toolchain_x86",
-    toolchain_type = "@bazel_tools//tools/cpp:toolchain_type",
-)
-
 # arm64 toolchain definition.
 android_cc_toolchain(
     name = "cc_toolchain_arm64",
@@ -173,23 +98,9 @@ android_cc_toolchain(
     toolchain_identifier = "arm64-toolchain",
 )
 
-toolchain(
-    name = "cc_toolchain_arm64_def",
-    exec_compatible_with = [
-        "//build/bazel/platforms/arch:x86_64",
-        "//build/bazel/platforms/os:linux",
-    ],
-    target_compatible_with = [
-        "//build/bazel/platforms/arch:arm64",
-        "//build/bazel/platforms/os:android",
-    ],
-    toolchain = ":cc_toolchain_arm64",
-    toolchain_type = "@bazel_tools//tools/cpp:toolchain_type",
-)
-
 # arm32 toolchain definition.
 android_cc_toolchain(
-    name = "cc_toolchain_arm32",
+    name = "cc_toolchain_arm",
     target_os = "android",
     target_arch = "arm",
     clang_version = ":clang",
@@ -204,20 +115,98 @@ android_cc_toolchain(
     toolchain_identifier = "arm-toolchain",
 )
 
-toolchain(
-    name = "cc_toolchain_arm32_def",
-    exec_compatible_with = [
-        "//build/bazel/platforms/arch:x86_64",
-        "//build/bazel/platforms/os:linux",
+# Toolchain to compile for the linux host.
+# TODO(b/186628704): automatically generate from Soong.
+android_cc_toolchain(
+    name = "cc_toolchain_x86_64_linux_host",
+    target_os = "linux_glibc",
+    target_arch = "x86_64",
+    clang_version = ":clang",
+    clang_version_directory = generated_constants.CLANG_DEFAULT_VERSION,
+    libclang_rt_builtin = _LIBCLANG_RT_PREBUILT_MAP["//build/bazel/platforms/os_arch:linux_glibc_x86_64"],
+    linker_flags = [
+        "-m64",
+        "-Wl,-z,noexecstack",
+        "-Wl,-z,relro",
+        "-Wl,-z,now",
+        "-Wl,--no-undefined-version",
     ],
-    target_compatible_with = [
-        "//build/bazel/platforms/arch:arm",
-        "//build/bazel/platforms/os:android",
+    target_flags = [
+        "-m64",
+        "-fdiagnostics-color",
+        "-Wa,--noexecstack",
+        "-fPIC",
+        "-U_FORTIFY_SOURCE",
+        "-D_FORTIFY_SOURCE=2",
+        "-fstack-protector",
+        # Workaround differences in inttypes.h between host and target.
+        # See bug 12708004.
+        "-D__STDC_FORMAT_MACROS",
+        "-D__STDC_CONSTANT_MACROS",
     ],
-    toolchain = ":cc_toolchain_arm32",
-    toolchain_type = "@bazel_tools//tools/cpp:toolchain_type",
+    toolchain_identifier = "x86_64-toolchain",
 )
 
+toolchain_type(name = "nocrt_toolchain")
+
+ARCHITECTURES = ["x86_64", "x86", "arm", "arm64"]
+
+# Device toolchains with crt libraries
+[
+    toolchain(
+        name = "cc_toolchain_%s_def" % arch,
+        exec_compatible_with = [
+            "//build/bazel/platforms/arch:x86_64",
+            "//build/bazel/platforms/os:linux",
+        ],
+        target_compatible_with = [
+            "//build/bazel/platforms/arch:%s" % arch,
+            "//build/bazel/platforms/os:android",
+        ],
+        toolchain = ":cc_toolchain_%s" % arch,
+        toolchain_type = "@bazel_tools//tools/cpp:toolchain_type",
+    ) for arch in ARCHITECTURES
+]
+
+# Device toolchains without crt libraries
+[
+    toolchain(
+        name = "cc_toolchain_%s_nocrt_def" % arch,
+        exec_compatible_with = [
+            "//build/bazel/platforms/arch:x86_64",
+            "//build/bazel/platforms/os:linux",
+        ],
+        target_compatible_with = [
+            "//build/bazel/platforms/arch:%s" % arch,
+            "//build/bazel/platforms/os:android",
+        ],
+        toolchain = ":cc_toolchain_%s_nocrt" % arch,
+        toolchain_type = ":nocrt_toolchain",
+    ) for arch in ARCHITECTURES
+]
+
+# Host toolchains for linux x86_64
+[
+    toolchain(
+        name = "%s_def" % toolchain_name,
+        exec_compatible_with = [
+            "//build/bazel/platforms/arch:x86_64",
+            "//build/bazel/platforms/os:linux",
+        ],
+        target_compatible_with = [
+            "//build/bazel/platforms/arch:x86_64",
+            "//build/bazel/platforms/os:linux",
+        ],
+        # TODO(b/181803350): Fix linux toolchain flag set, as the current flags are for android.
+        toolchain = toolchain_name,
+        toolchain_type = toolchain_type,
+    ) for (toolchain_name, toolchain_type) in
+    [
+        ("cc_toolchain_x86_64_linux_host", "@bazel_tools//tools/cpp:toolchain_type"),
+        ("cc_toolchain_x86_64_linux_host_nocrt", "nocrt_toolchain"),
+    ]
+]
+
 cc_import(
     name = "libclang_rt",
     static_library = select(_LIBCLANG_RT_PREBUILT_MAP),