Fix compilation with Xcode version of clang.

build/toolchain/toolchain.gni

Index: build/toolchain/toolchain.gni
diff --git a/build/toolchain/toolchain.gni b/build/toolchain/toolchain.gni
index fbaf48066840ae7f51436e87ff8e52b23091fc4f..1f32ebd38c24a7c19915b328e07b1b07a2b1f475 100644
--- a/build/toolchain/toolchain.gni
+++ b/build/toolchain/toolchain.gni
@@ -49,8 +49,10 @@ declare_args() {
   }
 }
 
-assert(!use_xcode_clang || is_ios,
-       "Using Xcode's clang is only supported in iOS builds")
+if (current_toolchain == default_toolchain) {
+  assert(!use_xcode_clang || is_ios,
+         "Using Xcode's clang is only supported in iOS builds")
+}

[Dirk Pranke, 2016/08/03 16:49:50]

This is probably relatively harmless (or even a good thing), but unless we
explicitly set use_xcode_clang=false in toolchain_args(), we'll probably end up
using xcode clang for host binaries as well.

So, this might be a bit clearer if the assert was (!use_xcode_clang ||
target_os=="ios").

[sdefresne, 2016/08/03 17:03:40]

The changes in build/toolchain/mac/BUILD.gn only check use_xcode_clang if
toolchain_os is "ios", so when building for iOS, we use the hermetic version of
clang for host_toolchain and xcode's clang for target toolchains.

I've changed the conditional as I agree it is cleaner.

 
 # Subdirectory within root_out_dir for shared library files.
 # TODO(agrieve): GYP sets this to "lib" for Linux & Android, but this won't work