[PATCH, Makefile.in] refine selftest recipes to restore mingw bootstrap

[Olivier Hainque <hainque at adacore dot com>]

Hello,

Bootstrap for mingw target configurations is failing today, with complaints
about an inexistant /dev/null.

The failing commands are issued by the selftest recipes in gcc/Makefile, using:

    SELFTEST_FLAGS = -nostdinc /dev/null -S -o /dev/null \
            -fself-test=$(srcdir)/testsuite/selftests

The attached patch is a proposal to fix this by resorting to "nul" instead of
"/dev/null" when the build machine name indicates a mingw setup.

It fixes the gcc-7 bootstrap in our Windows setup (i686-pc-mingw32), and passes
bootstrap and regression tests on x86_64-linux.

OK to commit ?

Thanks much in advance,

With Kind Regards,

Olivier

2017-11-24  Olivier Hainque  <hainque@adacore.com>

	* Makefile.in (SELFTEST_FLAGS): Use nul instead of /dev/null
	on mingw build hosts.

Attachment: dev_null.diff
Description: Binary data