Introduce build/config/external_libraries.gni

Add a more-centralized location for specifying whether external
libraries are installed on the system. This will allow multiple
applications access to config common to the entire build.

NOTE: GN config() targets were not used since they cannot be used from
an import (a .gni file). Also, we want the users of the openscreen
library to be able to auto-generate args.gn from whatever
"autoconf"-like tool they choose to use rather than have to manually
modify multiple BUILD.gn files.

Bug: openscreen:92
Change-Id: If238c83aaa841fbcfb7be18c3b82b6ca020f7932
Reviewed-on: https://chromium-review.googlesource.com/c/openscreen/+/1989114
Reviewed-by: Jordan Bayles <jophba@chromium.org>
Commit-Queue: Yuri Wiitala <miu@chromium.org>

1 files changed, 33 insertions, 0 deletions

diff --git a/build/config/external_libraries.gni b/build/config/external_libraries.gni
new file mode 100644
index 00000000..fe283535
--- /dev/null
+++ b/build/config/external_libraries.gni
@@ -0,0 +1,33 @@
+# Copyright 2019 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+declare_args() {
+  # FFMPEG: If installed on the system, set have_ffmpeg to true. This also
+  # requires the FFMPEG headers be installed. For example, on Debian-like
+  # systems, the following should install everything needed:
+  #
+  #   sudo apt-get install libavcodec libavcodec-dev \
+  #                        libavformat libavformat-dev \
+  #                        libavutil libavutil-dev \
+  #                        libswresample libswresample-dev
+  have_ffmpeg = false
+  ffmpeg_libs = [
+    "avcodec",
+    "avformat",
+    "avutil",
+    "swresample",
+  ]
+  ffmpeg_include_dirs = []  # Add only if headers are at non-standard locations.
+  ffmpeg_lib_dirs = []  # Add only if libraries are at non-standard locations.
+
+  # libsdl2: If installed on the system, set have_libsdl2 to true. This also
+  # requires the libSDL2 headers be installed. For example, on Debian-like
+  # systems, the following should install everything needed:
+  #
+  #   sudo apt-get install libsdl2-2.0 libsdl2-dev
+  have_libsdl2 = false
+  libsdl2_libs = [ "SDL2" ]
+  libsdl2_include_dirs = []  # Add only if headers are at non-standard locations.
+  libsdl2_lib_dirs = []  # Add only if libraries are at non-standard locations.
+}