llc: Eliminate a use of getDarwinMajorNumber().

- As before, there is a minor semantic change here (evidenced by the test
   change) for Darwin triples that have no version component. I debated changing
   the default behavior of isOSVersionLT, but decided it made more sense for
   triples to be explicit.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@129805 91177308-0d34-0410-b5e6-96231b3b80d8

tools/llc/llc.cpp

@@ -278,18 +278,10 @@ int main(int argc, char **argv) {
 
   if (DisableDotLoc)
     Target.setMCUseLoc(false);
-  if (TheTriple.getOS() == Triple::Darwin) {
-    switch (TheTriple.getDarwinMajorNumber()) {
-    case 7:
-    case 8:
-    case 9:
-      // disable .loc support for older darwin OS.
-      Target.setMCUseLoc(false);
-      break;
-    default:
-      break;
-    }
-  }
+
+  // Disable .loc support for older OS X versions.
+  if (TheTriple.isOSX() && TheTriple.isOSXVersionLT(10, 5))
+    Target.setMCUseLoc(false);
 
   // Figure out where we are going to send the output...
   OwningPtr<tool_output_file> Out