Use the simpler version of llvm::sys::fs::exists.

In all these cases it looks like the intention was to handle error in a similar
way to the file not existing.

llvm-svn: 217614
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 36d5a54..ced08fb 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -7626,12 +7626,9 @@
                                    const InputInfoList &Inputs,
                                    const ArgList &Args,
                                    const char *LinkingOutput) const {
-  bool UseGCC47 = false;
   const Driver &D = getToolChain().getDriver();
   ArgStringList CmdArgs;
-
-  if (llvm::sys::fs::exists("/usr/lib/gcc47", UseGCC47))
-    UseGCC47 = false;
+  bool UseGCC47 = llvm::sys::fs::exists("/usr/lib/gcc47");
 
   if (!D.SysRoot.empty())
     CmdArgs.push_back(Args.MakeArgString("--sysroot=" + D.SysRoot));