pgsql: Don't unset MAKEFLAGS in non-GNU Makefile.

Don't unset MAKEFLAGS in non-GNU Makefile.

It's useful to be able to pass down options like -s and -j.

Back-patch to 9.5, like commit a76200de.

Discussion: https://postgr.es/m/CA%2BhUKG%2Be1M8-BbL%3DPqhTp6oO6XPO6%2Bs9WGQMLfbuZ%3DG9CtzyXg%40mail.gmail.com

Branch
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REL9_6_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/3a3b361ccbd8563f3b416e5ab5077b73dccd80e8

Modified Files
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Makefile | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)