[driver] Pass a resource dir without the '/../' part.

This get the resource dir string to match with the one from libclang (which is not adding '/../'),
and allows clang to accept a modules-enabled PCH that was created by libclang.

llvm-svn: 296262
diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
index b8ae7e4..6defb20 100644
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -79,7 +79,8 @@
     llvm::sys::path::append(P, ClangResourceDir);
   } else {
     StringRef ClangLibdirSuffix(CLANG_LIBDIR_SUFFIX);
-    llvm::sys::path::append(P, "..", Twine("lib") + ClangLibdirSuffix, "clang",
+    P = llvm::sys::path::parent_path(Dir);
+    llvm::sys::path::append(P, Twine("lib") + ClangLibdirSuffix, "clang",
                             CLANG_VERSION_STRING);
   }
   ResourceDir = P.str();