mac: Let remoting_host_prefpane link with libc++.

Once I figured out the static library libc++ build story, I'll likely move
this target back to libstdc++, but for now it works with libc++, so use the
libc++ in component build like every other target does.

See comment 7 on the linked bug for why the file in overrides/ is needed.

BUG=544531

Review URL: https://codereview.chromium.org/1411553005

Cr-Original-Commit-Position: refs/heads/master@{#354824}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: bed1d0c35e86bc859f94573b4c15d18c17994383
diff --git a/README.chromium b/README.chromium
index b6581c6..5e7dac6 100644
--- a/README.chromium
+++ b/README.chromium
@@ -12,6 +12,6 @@
 
 Local modifications:
 The overrides are used to eliminate static initializers in json_value.cpp and
-json_reader.cpp adds includes for <string> and <istream> to build on libc++,
-and to change some one-bit bit fields to unsigned so that they can hold the
-'1' values that are stored in them.
+json_reader.cpp adds includes for <string> and <istream> to build on libc++
+(https://llvm.org/PR25232), and to change some one-bit bit fields to unsigned
+so that they can hold the '1' values that are stored in them.