crt: Build crt sources with -D__USE_MINGW_ANSI_STDIO=0

This fixes lots of warnings like these:

stdio/snprintf.c:9:13: warning: no previous prototype for function '__ms_snprintf' [-Wmissing-prototypes]
stdio/vwscanf.c:15:10: warning: implicit declaration of function '__ms_vfwscanf' is invalid in C99 [-Wimplicit-function-declaration]

Signed-off-by: Martin Storsjö <martin@martin.st>
1 file changed