mingw: drop the -D_USE_32BIT_TIME_T option

This option was added in fa93bb2 (MinGW: Fix stat definitions to
work with MinGW runtime version 4.0, 2013-09-11), i.e. a _long_ time
ago. So long, in fact, that it still targeted MinGW. But we switched to
mingw-w64 in 2015, which seems not to share the problem, and therefore
does not require a fix.

Even worse: This flag is incompatible with UCRT64, which we are about to
support by way of upstreaming `mingw-w64-git` to the MSYS2 project, see
msys2/MINGW-packages#26470 for details.

So let's send that option into its well-deserved retirement.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

config.mak.uname

@@ -761,7 +761,6 @@ ifeq ($(uname_S),MINGW)
 		HOST_CPU = aarch64
 		BASIC_LDFLAGS += -Wl,--pic-executable,-e,mainCRTStartup
         else
-		COMPAT_CFLAGS += -D_USE_32BIT_TIME_T
 		BASIC_LDFLAGS += -Wl,--large-address-aware
         endif
 	CC = gcc