pgsql: Fix order of -I switches for building pg_regress.o.

Fix order of -I switches for building pg_regress.o.

We need the -I switch for libpq_srcdir to come before any -I switches
injected by configure. Otherwise there is a risk of pulling in a
mismatched version of libpq_fe.h from someplace like
/usr/local/include, if the platform has another Postgres version
installed there. This evidently accounts for today's buildfarm
failures on "anaconda".

In principle the -I switch for src/port/ is at similar hazard, and has
been for a very long time. But the only .h files we keep there are
pg_config_paths.h and pthread-win32.h, neither of which get installed
on Unix-ish systems, so the odds of picking up a conflicting header
seem pretty small. That doubtless accounts for the lack of prior
reports.

Back-patch to v17 where pg_regress acquired a build dependency on
libpq_fe.h. We could go back further to fix the hazard for src/port/
in older branches, but it seems unlikely to be worth troubling over.

Reported-by: Nathan Bossart <nathandbossart(at)gmail(dot)com>
Author: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Discussion: https://postgr.es/m/Z-MhRzoc7t-nPUQG@nathan
Backpatch-through: 17

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/cb36f8ec2124b0c495da057a2f55735fe858be0e

Modified Files
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src/test/regress/GNUmakefile | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)