Use automatic color option with the latest clang.

Bug: 18187181

Now that I checked in the latest prebuilts, clang will automatically use
color on terminals and no color on redirection to files or non-terminals.

Change-Id: I9be00c44947946cc18ce59c936b7f45d0ce2b6fc
diff --git a/core/clang/config.mk b/core/clang/config.mk
index 4393340..acb425d 100644
--- a/core/clang/config.mk
+++ b/core/clang/config.mk
@@ -45,8 +45,7 @@
 # Workaround for ccache with clang.
 # See http://petereisentraut.blogspot.com/2011/05/ccache-and-clang.html.
 CLANG_CONFIG_EXTRA_CFLAGS += \
-  -Wno-unused-command-line-argument \
-  -fcolor-diagnostics
+  -Wno-unused-command-line-argument
 
 CLANG_CONFIG_UNKNOWN_CFLAGS := \
   -finline-limit=64 \