bug#25283: grep: (standard input): invalid argument when run from make

[Paul Eggert]

Thanks for reporting that problem. I wonder why GNU 'make' sets stdout to append 
mode? That surprises me, and I don't see where POSIX allows it. Anyway, it's 
clearly a bug in 'grep' no matter what 'make' is doing. I wrote up a test case 
for the bug and installed the attached, which is a bit more conservative than 
the patch you submitted.

0001-grep-fix-bug-with-.-grep-pat-dev-null.txt
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