llvm-mc: Fix target selection for --disassemble to use GetTarget.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@98973 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/llvm-mc/llvm-mc.cpp b/tools/llvm-mc/llvm-mc.cpp
index 3778bc9..62391b2 100644
--- a/tools/llvm-mc/llvm-mc.cpp
+++ b/tools/llvm-mc/llvm-mc.cpp
@@ -318,13 +318,9 @@
 }
 
 static int DisassembleInput(const char *ProgName) {
-  std::string Error;
-  const Target *TheTarget = TargetRegistry::lookupTarget(TripleName, Error);
-  if (TheTarget == 0) {
-    errs() << ProgName << ": error: unable to get target for '" << TripleName
-    << "', see --version and --triple.\n";
+  const Target *TheTarget = GetTarget(ProgName);
+  if (!TheTarget)
     return 0;
-  }
   
   std::string ErrorMessage;