[m-rev.] for review: Update README.MinGW regarding MSYS2 and x86_64.

[Julien Fischer]

Hi Peter,

On Tue, 25 Aug 2015, Peter Wang wrote:

> If anyone would care to try to reproduce the build on i686 or x86_64,
> that would be great.

The only additional issue I encountered is that on my system there are
three MSYS2 items under the start menu:

     * MinGW-w64 Win32 Shell
     * MinGW-w64 Win64 Shell
     * MSYS2

If you select the last one then GCC doesn't appear to be in the PATH
by default.  I also had to apply the following patch:

--------------------

diff --git a/boehm_gc/Makefile.direct b/boehm_gc/Makefile.direct
index 23c12bb..58e0cd7 100644
--- a/boehm_gc/Makefile.direct
+++ b/boehm_gc/Makefile.direct
@@ -235,7 +235,7 @@ all: gc.a gctest
  # Mercury-specific: clear DESTDIR
  $(AO_INSTALL_DIR):
         CC="$(CC)" AR="$(AR)" RANLIB="$(RANLIB)" MAKE=$(MAKE) DESTDIR= \
-          $(srcdir)/build_atomic_ops.sh --host=$(FULLARCH)
+          $(srcdir)/build_atomic_ops.sh --build=$(FULLARCH) --host=$(FULLARCH)

  LEAKFLAGS=$(CFLAGS) -DFIND_LEAK

--------------

I'm not quite sure *why* I had I to do that, although I suspect the
reason is that the versions of config.guess and config.sub under the
boehm_gc directory are *very* old (from ~2009).

Julien.