appendSuffix: don't append a dot when the suffix is empty.

Additionally, move the implementation of appendSuffix to Path.cpp: it is
platform-independent.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@118089 91177308-0d34-0410-b5e6-96231b3b80d8

lib/System/Path.cpp

@@ -195,6 +195,21 @@ StringRef Path::GetDLLSuffix() {
   return &(LTDL_SHLIB_EXT[1]);
 }
 
+bool
+Path::appendSuffix(StringRef suffix) {
+  if (!suffix.empty()) {
+    std::string save(path);
+    path.append(".");
+    path.append(suffix);
+    if (!isValid()) {
+      path = save;
+      return false;
+    }
+  }
+
+  return true;
+}
+
 bool
 Path::isBitcodeFile() const {
   std::string actualMagic;