[CMake] Add PACKAGE_VENDOR for customizing version output

[beanz]

Summary

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

include/llvm/Config/config.h.cmake

 #cmakedefine PACKAGE_STRING "${PACKAGE_STRING}"
 
 /* Define to the one symbol short name of this package. */
 #undef PACKAGE_TARNAME
 
 /* Define to the version of this package. */
 #cmakedefine PACKAGE_VERSION "${PACKAGE_VERSION}"
 
+/* Define to the vendor of this package. */
+#cmakedefine PACKAGE_VENDOR "${PACKAGE_VENDOR}"
+
 /* Define as the return type of signal handlers (`int' or `void'). */
 #cmakedefine RETSIGTYPE ${RETSIGTYPE}
 
 /* Define to 1 if the `S_IS*' macros in <sys/stat.h> do not work properly. */
 #undef STAT_MACROS_BROKEN
 
 /* Define to 1 if you have the ANSI C header files. */
 #undef STDC_HEADERS

lib/Support/CommandLine.cpp

 
 static std::vector<void (*)()> *ExtraVersionPrinters = nullptr;
 
 namespace {
 class VersionPrinter {
 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
     OS << "\n  ";
 #ifndef __OPTIMIZE__
     OS << "DEBUG build";
 #else
     OS << "Optimized build";