Darwin-embedded: find correct libclang_rt for embedded targets.

This refactors some of the Darwin toolchain classification to give a more solid
distinction between the three primary Darwin platforms (OS X, IOS and IOS
simulator) so that a 4th choice can be added temporarily: embedded MachO
targets.

Longer term, this support will be factored out into a separate class and no
longer classified as "darwin-eabi", but the refactoring should still be useful.

llvm-svn: 197148
diff --git a/clang/lib/Driver/Tools.h b/clang/lib/Driver/Tools.h
index e4b1fdf..b2dd6d9 100644
--- a/clang/lib/Driver/Tools.h
+++ b/clang/lib/Driver/Tools.h
@@ -606,6 +606,10 @@
   };
 } // end namespace visualstudio
 
+namespace arm {
+  StringRef getARMFloatABI(const Driver &D, const llvm::opt::ArgList &Args,
+                         const llvm::Triple &Triple);
+}
 namespace XCore {
   // For XCore, we do not need to instantiate tools for PreProcess, PreCompile and Compile.
   // We simply use "clang -cc1" for those actions.