test-grep-lint is uncomfortably slow

test-grep-lint is uncomfortably slow

[Junio C Hamano]

Does anyone else feel that make test takes too long to start?  There
is a noticeable pause after "rm -f -r 'test-results'" before the first
line of real output is shown.  The time in between is likely spent on
make test-lint.

Here is a time to run "make test-lint" 5 times in a row.

$ time sh -c 'for c in 1 2 3 4 5; do make test-lint; done'
real    0m49.221s
user    1m37.796s
sys     0m4.597s

If we revert the merge c9a92e239f (Merge branch 'mm/test-grep-lint',
2026-07-19) to disable the grep-lint, it becomes somewhat tolerable.

$ time sh -c 'for c in 1 2 3 4 5; do make test-lint; done'
real    0m9.166s
user    0m59.156s
sys     0m2.887s

Is this something we can make go faster?  

Thanks.