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: I38a858b1d41d6567bdd0fbc91b307b0270ab51b1
diff --git a/cc/config/global.go b/cc/config/global.go
index ff5ab05..e547c3f 100644
--- a/cc/config/global.go
+++ b/cc/config/global.go
@@ -68,10 +68,6 @@
 		// 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",