[PATCH] Allow clang-cl to automatically use lld instead of forcing the MSVC linker

[Nico Weber]

================
Comment at: lib/Driver/Tools.cpp:7990
@@ +7989,3 @@
+  } else {
+    ld_value = "link";
+  }
----------------
Somewhat tangential: It would be nice if clang could default to lld-link if link.exe isn't found. If I'm using clang-cl targeting Windows on non-Windows, and lld-link is in the same directory as clang-cl, it'd be great if clang-cl would then transparently use lld-link to link my PE binary instead of telling me "unable to execute command: Executable "link.exe" doesn't exist!"

(Not sure if this should be part of this change, but it's in the same code at least.)

http://reviews.llvm.org/D6428