mac: remove libc++-static 10.6 compatibility hack

build/config/compiler/BUILD.gn

Index: build/config/compiler/BUILD.gn
diff --git a/build/config/compiler/BUILD.gn b/build/config/compiler/BUILD.gn
index ad6cc65677497ad7fd377cb9b144d32eff52c791..ce0bf4dbc3d9f4321b737836a70df20a81df39e0 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -403,37 +403,6 @@ config("compiler") {
     cflags_cc += [ "-std=c++11" ]
   }
 
-  if (is_mac) {
-    # Tell the compiler to use libc++'s headers and the linker to link
-    # against libc++.  The latter part normally requires OS X 10.7,
-    # but we still support running on 10.6.  How does this work?  Two
-    # parts:
-    # 1. Chromium's clang doesn't error on -mmacosx-version-min=10.6
-    #    combined with -stdlib=libc++ (it normally silently produced a
-    #    binary that doesn't run on 10.6)
-    # 2. Further down, library_dirs is set to
-    #    third_party/libc++-static, which contains a static
-    #    libc++.a library.  The linker then links against that instead
-    #    of against /usr/lib/libc++.dylib when it sees the -lc++ flag
-    #    added by the driver.
-    #
-    # In component builds, just link to the system libc++.  This has
-    # the effect of making everything depend on libc++, which means
-    # component-build binaries won't run on 10.6 (no libc++ there),
-    # but for a developer-only configuration that's ok.  (We don't
-    # want to raise the deployment target yet so that official and
-    # dev builds have the same deployment target.  This affects
-    # things like which functions are considered deprecated.)
-    cflags_cc += [ "-stdlib=libc++" ]

[Mark Mentovai, 2016/09/12 18:33:26]

We still need -stdlib, until we finally get our deployment target bumped to 10.8
or higher.

-    ldflags += [ "-stdlib=libc++" ]
-    if (!is_component_build && !is_asan) {

[Mark Mentovai, 2016/09/12 18:33:26]

But this stuff, and the long comment in this block, are no longer necessary.

-      ldflags += [
-        "-L",
-        rebase_path("//third_party/libc++-static", root_build_dir),
-      ]
-    }
-  }
-
   # Add flags for link-time optimization. These flags enable
   # optimizations/transformations that require whole-program visibility at link
   # time, so they need to be applied to all translation units, and we may end up