llvm-lto2: Changed version main command to --version

Author: fnriv

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

@@ -1,7 +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 --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 version\n";
+  errs() << "Available subcommands: dump-symtab run print-guid --version\n";
   return 1;
 }
 
@@ -616,7 +616,7 @@ int main(int argc, char **argv) {
     outs() << GlobalValue::getGUIDAssumingExternalLinkage(argv[2]) << '\n';
     return 0;
   }
-  if (Subcommand == "version") {
+  if (Subcommand == "--version") {
     cl::PrintVersionMessage();
     return 0;
   }