MachO: perform ARM ABI detection even for non-Darwin triples.

When "-arch armv7m" is specified, we want "aapcs", for example.

rdar://problem/16581138

llvm-svn: 209434
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 534afc5..e51cb1b 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -771,7 +771,7 @@
   const char *ABIName = nullptr;
   if (Arg *A = Args.getLastArg(options::OPT_mabi_EQ)) {
     ABIName = A->getValue();
-  } else if (Triple.isOSDarwin()) {
+  } else if (Triple.isOSBinFormatMachO()) {
     // The backend is hardwired to assume AAPCS for M-class processors, ensure
     // the frontend matches that.
     if (Triple.getEnvironment() == llvm::Triple::EABI ||