Prefer ranlib mode over ar mode.

[ed]

Summary

For CloudABI's toolchain I have a symlink that goes from <target>-ar and
<target>-ranlib to LLVM's ar binary, to mimick GNU Binutils' naming
scheme. The problem is that if we're targetting ARM64, the name of the
ranlib executable is aarch64-unknown-cloudabi-ranlib. This already
contains the string "ar".

Let's move the "ranlib" test above the "ar" test. It's not that likely
that we're going to see operating systems or harwdare architectures that
are called "ranlib".

[• rafael]

LGTM.

llvm/trunk/tools/llvm-ar/llvm-ar.cpp

int main(int argc, char **argv) {
 
   // Have the command line options parsed and handle things
   // like --help and --version.
   cl::ParseCommandLineOptions(argc, argv,
     "LLVM Archiver (llvm-ar)\n\n"
     "  This program archives bitcode files into single libraries\n"
   );
 
-  if (Stem.find("ar") != StringRef::npos)
-    return ar_main();
   if (Stem.find("ranlib") != StringRef::npos)
     return ranlib_main();
+  if (Stem.find("ar") != StringRef::npos)
+    return ar_main();
   fail("Not ranlib, ar or lib!");
 }