[Zucchini] Buildflag control of architectures

Allows Zucchini to be built with only a subset of architectures enabled
this saves on binary size at the cost of flexibility. The idea is that
only the desired architectures would be compiled for a particular
usecases. For example the Windows setup.exe only needs Windows support.

Expected savings as a percent of total binary size at present
(868.5 kB non-debug):
- Remove DEX 3.13% (841.3 kB)
- Remove Win 6.00% (816.4 kB)
- Only Raw 9.13% (789.2 kB)

Note that in the case of Raw saving could be made significantly higher
by entirely removing the dependence on references and reference
projection. However, at present the additional messiness of the
additional buildflags all over the codebase is not worth the
maintenance costs.

Bug: 835007
Change-Id: I091cb9d76e8473340374be1a33a5df48137a3067
Reviewed-on: https://chromium-review.googlesource.com/1037922
Commit-Queue: Calder Kitagawa <ckitagawa@google.com>
Reviewed-by: Greg Thompson <grt@chromium.org>
Reviewed-by: Samuel Huang <huangs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#556802}
NOKEYCHECK=True
GitOrigin-RevId: f0545bf20576afb65f9bbc493ea9b4d5d42c4738

1 files changed, 14 insertions, 0 deletions

diff --git a/BUILD.gn b/BUILD.gn
index 800216e..f36c949 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -2,9 +2,22 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//build/buildflag_header.gni")
 import("//chrome/process_version_rc_template.gni")
 import("//testing/test.gni")
 
+buildflag_header("buildflags") {
+  header = "buildflags.h"
+
+  # Disable DEX on Windows Official Builds.
+  _enable_dex = !(is_win && is_official_build)
+  _enable_win = true
+  flags = [
+    "ENABLE_DEX=$_enable_dex",
+    "ENABLE_WIN=$_enable_win",
+  ]
+}
+
 static_library("zucchini_lib") {
   sources = [
     "abs32_utils.cc",
@@ -79,6 +92,7 @@ static_library("zucchini_lib") {
   ]
 
   deps = [
+    ":buildflags",
     "//base",
   ]
 }