Since Make version 4.4, MAKEFLAGS also contains long options and
overridden variables on the command-line[1].
[1]: https://git.savannah.gnu.org/cgit/make.git/tree/NEWS?h=4.4#n67
This means that parsing by filtering out '--%' doesn't work reliably
anymore, since it doesn't remove overrides:
Running 'make VAR=quacks' gives 'MAKEFLAGS=" -- VAR=quacks"', and
'checkflags' would understand that flags -q, -s, ... were set.
This would get transmitted below into 'QUIET_FLAGS' and
'QUESTION_FLAG', then passed to the 'genVersionHeader.pl' as '-i' and
'-q'.
The result would be that 'genVersionHeader.pl' would never create the
version header (only check for its up-to-date status), leading to
confusing errors:
../misc/epicsRelease.c:25:32: error: expected ')' before 'EPICS_VCS_VERSION'
25 | printf ( "## %s\n", "Rev. " EPICS_VCS_VERSION );
| ~ ^~~~~~~~~~~~~~~~~~
The NEWS file[1] recommends using 'firstword', but unfortunately this is
not compatible with GNUMake < 3.82.
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