[PATCH] Mingw-w64 driver for clang

[Ruben Van Boxem]

I have tested basic functionality on Windows using the MinGW-Builds toolchains. Couldn't cleanly test the MSYS2 built ones, but I'm assuming they will function as well. Will try to test on Archlinux tomorrow.

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Comment at: lib/Driver/MinGWToolChain.cpp:48
@@ +47,3 @@
+      GCCVersion = llvm::sys::path::filename(entry->path());
+    // TODO report error: "no MinGW-w64 GCC installation found"
+  }
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I chose the fast solution here. There really should be a better way to handle this. Although in the long run the GCC dependence should go away (once libc++ is a viable alternative). So really all that needs to be put here is a decent way to handle the error here (e.g. just a message that is output to the console, probably a diagnostic of some kind).

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Comment at: lib/Driver/ToolChains.h:764
@@ +763,3 @@
+  bool isPICDefaultForced() const override;
+  bool UseSEHExceptions() const override;
+
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This "override" needs to be removed. GCC complains about it, and it is right to do so.

http://reviews.llvm.org/D5268