Move cobalt variables to build_config.h (#4313)

b/375617387

build/build_config.h

@@ -254,6 +254,18 @@
 #define BUILDFLAG_INTERNAL_IS_OZONE() (0)
 #endif
 
+#if defined(IS_COBALT)
+#define BUILDFLAG_INTERNAL_IS_COBALT() (1)
+#else
+#define BUILDFLAG_INTERNAL_IS_COBALT() (0)
+#endif
+
+#if defined(USE_STARBOARD)
+#define BUILDFLAG_INTERNAL_USE_STARBOARD() (1)
+#else
+#define BUILDFLAG_INTERNAL_USE_STARBOARD() (0)
+#endif
+
 // Compiler detection. Note: clang masquerades as GCC on POSIX and as MSVC on
 // Windows.
 #if defined(__GNUC__)

cobalt/build/configs/BUILD.gn

@@ -17,6 +17,11 @@ config("cobalt_config") {
   if (current_toolchain == starboard_toolchain) {
     configs += [ "//${starboard_path}/platform_configuration" ]
   }
+
+  defines = [
+    "IS_COBALT",
+    "USE_STARBOARD",
+  ]
 }
 
 config("default_includes") {

starboard/build/BUILD.gn

@@ -13,27 +13,31 @@
 # limitations under the License.
 
 import("//build/buildflag_header.gni")
-import("//cobalt/build/configs/cobalt.gni")
 import("//cobalt/build/configs/variables.gni")
-
-declare_args() {
-  use_starboard = target_os != "android"
-  use_starboard_media = is_cobalt
-  use_evergreen = false
-}
+import("//starboard/build/buildflags.gni")
 
 # To use these build flags from i.e. "foo.cc", add a dependency from the target
-# containing "foo.cc" on this target, then have "foo.cc" include
+# containing "foo.cc" on this target, then have "foo.cc" conditionally include
 # "starboard/build/starboard_buildflags.h". After that you can use i.e.
-# BUILDFLAG(USE_STARBOARD) in your code.
+# BUILDFLAG(USE_STARBOARD_MEDIA) in your code.
+#
+# Example:
+#
+# #include "build/build_config.h"
+# #if BUILDFLAG(IS_COBALT)
+# #include "starboard/build/starboard_buildflags.h"
+# #endif
+#
+# #if BUILDFLAG(USE_STARBOARD_MEDIA)
+# // Do something
+# #endif
+#
 buildflag_header("starboard_buildflags") {
   header = "starboard_buildflags.h"
 
   flags = [
-    "USE_STARBOARD=$use_starboard",
     "USE_STARBOARD_MEDIA=$use_starboard_media",
     "USE_EVERGREEN=$use_evergreen",
-    "IS_COBALT=$is_cobalt",
     "IS_MODULAR_BUILD=$sb_is_modular",
   ]
 }

starboard/build/buildflags.gni

@@ -0,0 +1,7 @@
+import("//cobalt/build/configs/cobalt.gni")
+
+declare_args() {
+  use_starboard = target_os != "android"
+  use_starboard_media = is_cobalt
+  use_evergreen = false
+}