Added version command for llvm-lto2

Author: fnriv

llvm/test/tools/llvm-lto2/version.test

@@ -0,0 +1,7 @@
+## Show that you can run version as a main command for llvm-lto2 
+## or a subcommand of llvm-lto2 run.
+
+RUN: llvm-lto2 version | Filecheck %s
+RUN: llvm-lto2 run --version | FileCheck %s 
+
+CHECK: version

llvm/tools/llvm-lto2/llvm-lto2.cpp

@@ -247,7 +247,7 @@ template <typename T> static T check(ErrorOr<T> E, std::string Msg) {
 }
 
 static int usage() {
-  errs() << "Available subcommands: dump-symtab run print-guid\n";
+  errs() << "Available subcommands: dump-symtab run print-guid version\n";
   return 1;
 }
 
@@ -616,5 +616,9 @@ int main(int argc, char **argv) {
     outs() << GlobalValue::getGUIDAssumingExternalLinkage(argv[2]) << '\n';
     return 0;
   }
+  if (Subcommand == "version") {
+    cl::PrintVersionMessage();
+    return 0;
+  }
   return usage();
 }