[Driver] Make -fno-common default for Fuchsia

We never want to generate common symbols on Fuchsia.

Differential Revision: https://reviews.llvm.org/D43545

llvm-svn: 325945

clang/lib/Driver/ToolChains/Clang.cpp

@@ -1306,6 +1306,8 @@ static bool isSignedCharDefault(const llvm::Triple &Triple) {
 static bool isNoCommonDefault(const llvm::Triple &Triple) {
   switch (Triple.getArch()) {
   default:
+    if (Triple.isOSFuchsia())
+      return true;
     return false;
 
   case llvm::Triple::xcore:

clang/test/Driver/fuchsia.c

@@ -10,6 +10,7 @@
 // CHECK: "-fuse-init-array"
 // CHECK: "-isysroot" "[[SYSROOT:[^"]+]]"
 // CHECK: "-internal-externc-isystem" "[[SYSROOT]]{{/|\\\\}}include"
+// CHECK: "-fno-common"
 // CHECK: {{.*}}ld.lld{{.*}}" "-z" "rodynamic"
 // CHECK: "--sysroot=[[SYSROOT]]"
 // CHECK: "-pie"