Handle Clang's change of defaults from -fcommon to -fno-common

Remove fcommon and make fno-common by default.

Bug: b/151457797
Test: make checkbuild
Change-Id: Ieb4c1e1bfff05fd0db894e8eab263fb31b376da9
diff --git a/cc/config/global.go b/cc/config/global.go
index 174b12c..a586a3f 100644
--- a/cc/config/global.go
+++ b/cc/config/global.go
@@ -67,10 +67,6 @@
 		// not emit the table by default on Android since NDK still uses GNU binutils.
 		"-faddrsig",
 
-		// Turn on -fcommon explicitly, since Clang now defaults to -fno-common. The cleanup bug
-		// tracking this is http://b/151457797.
-		"-fcommon",
-
 		// Help catch common 32/64-bit errors.
 		"-Werror=int-conversion",
 
@@ -253,6 +249,8 @@
 	// (anything for which IsThirdPartyPath() in build/soong/android/paths.go
 	// returns true - includes external/, most of vendor/ and most of hardware/)
 	noOverrideExternalGlobalCflags = []string{
+		// http://b/151457797
+		"-fcommon",
 		// http://b/191699019
 		"-Wno-format-insufficient-args",
 		// http://b/296321145