[m-rev.] diff: fix a configure script problem with MinGW64

[Julien Fischer]

Fix a configure script problem with MinGW64.

configure.ac:
	Make a configure check more specific: we should not
	attempt to link against libpthread just because $host
	matches  "*mingw*".  That doesn't (currently) work
	for x86_64-w64-mingw32.

Julien.

diff --git a/configure.ac b/configure.ac
index 2143b03..a7f7bc3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2966,7 +2966,11 @@ case "$host" in
         esac
         ;;

-    *mingw*)
+    # NOTE: do *not* attempt to use pthreads if we are cross compiling
+    # with the x86_64-w64-mingw32 GCC.
+    # XXX we we will need to do something different here when we support
+    # threads on 64-bit Windows.
+    i*86-pc-mingw*)
         THREAD_LIBS=""
         case "$mercury_cv_cc_type" in
             msvc)