clar: avoid compile error with mingw-w64

When using mingw-w64 to compile the code, and using `_stat()`, it is
necessary to use `struct _stat`, too, and not `struct stat` (as the
latter is incompatible with the "dashed" version because it is limited
to 32-bit time types for backwards compatibility).

Signed-off-by: Johannes Schindelin <[email protected]>
Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: dscho

t/unit-tests/clar/clar.c

@@ -68,7 +68,7 @@
 #		define PRIxZ "Ix"
 #	endif
 
-#	if defined(_MSC_VER) || defined(__MINGW32__)
+#	if defined(_MSC_VER) || (defined(__MINGW32__) && !defined(__MINGW64_VERSION_MAJOR))
 	typedef struct stat STAT_T;
 #	else
 	typedef struct _stat STAT_T;