Make the integrated assembler the default for cygwin/mingw too.

The integrated assembler was already the default for win32. It is now able
to handle a clang bootstrap on mingw, so make it the default.

llvm-svn: 195676
diff --git a/clang/lib/Driver/ToolChains.cpp b/clang/lib/Driver/ToolChains.cpp
index d9ad587..09afc1e 100644
--- a/clang/lib/Driver/ToolChains.cpp
+++ b/clang/lib/Driver/ToolChains.cpp
@@ -1612,6 +1612,11 @@
   return false;
 }
 
+bool Generic_GCC::IsIntegratedAssemblerDefault() const {
+  return getTriple().getArch() == llvm::Triple::x86 ||
+    getTriple().getArch() == llvm::Triple::x86_64;
+}
+
 /// Hexagon Toolchain
 
 std::string Hexagon_TC::GetGnuDir(const std::string &InstalledDir) {