Fix standalone ich_descriptor_tool compilation with MinGW and DJGPP

TARGET_OS as well as EXEC_SUFFIX were only set when called via the
main makefile and even then __USE_MINGW_ANSI_STDIO was not set
for MinGW.

While at it, also replace the hardcoded gnu_printf printf format
attribute with __MINGW_PRINTF_FORMAT which is set according to
__USE_MINGW_ANSI_STDIO respectively.

Change-Id: Id146f5ba06a0e510397c6f32a2bd7c819a405a25
Signed-off-by: Stefan Tauner <stefan.tauner@gmx.at>
Reviewed-on: https://review.coreboot.org/21838
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/22336
2 files changed