[CMake] Add PACKAGE_VENDOR for customizing version output

Summary: This change adds a PACKAGE_VENDOR variable. When set it makes the version output more closely resemble the clang version output.

Reviewers: aprantl, bogner

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D18159

llvm-svn: 263566
diff --git a/llvm/lib/Support/CommandLine.cpp b/llvm/lib/Support/CommandLine.cpp
index b0867b4..73792ef 100644
--- a/llvm/lib/Support/CommandLine.cpp
+++ b/llvm/lib/Support/CommandLine.cpp
@@ -1756,8 +1756,12 @@
 public:
   void print() {
     raw_ostream &OS = outs();
-    OS << "LLVM (http://llvm.org/):\n"
-       << "  " << PACKAGE_NAME << " version " << PACKAGE_VERSION;
+#ifdef PACKAGE_VENDOR
+    OS << PACKAGE_VENDOR << " ";
+#else
+    OS << "LLVM (http://llvm.org/):\n  ";
+#endif
+    OS << PACKAGE_NAME << " version " << PACKAGE_VERSION;
 #ifdef LLVM_VERSION_INFO
     OS << " " << LLVM_VERSION_INFO;
 #endif