Use the simpler is_directory.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@186487 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Driver/Driver.cpp b/lib/Driver/Driver.cpp
index 41b6387..f49e790 100644
--- a/lib/Driver/Driver.cpp
+++ b/lib/Driver/Driver.cpp
@@ -1569,8 +1569,7 @@
   // attempting to use this prefix when looking for program paths.
   for (Driver::prefix_list::const_iterator it = PrefixDirs.begin(),
        ie = PrefixDirs.end(); it != ie; ++it) {
-    bool IsDirectory;
-    if (!llvm::sys::fs::is_directory(*it, IsDirectory) && IsDirectory) {
+    if (llvm::sys::fs::is_directory(*it)) {
       SmallString<128> P(*it);
       llvm::sys::path::append(P, TargetSpecificExecutable);
       if (llvm::sys::fs::can_execute(Twine(P)))