pgsql: Suppress warning about stack_base_ptr with late-model GCC.

Suppress warning about stack_base_ptr with late-model GCC.

GCC 12 complains that set_stack_base is storing the address of
a local variable in a long-lived pointer. This is an entirely
reasonable warning (indeed, it just helped us find a bug);
but that behavior is intentional here. We can work around it
by using __builtin_frame_address(0) instead of a specific local
variable; that produces an address a dozen or so bytes different,
in my testing, but we don't care about such a small difference.
Maybe someday a compiler lacking that function will start to issue
a similar warning, but we'll worry about that when it happens.

Patch by me, per a suggestion from Andres Freund. Back-patch to
v12, which is as far back as the patch will go without some pain.
(Recently-established project policy would permit a back-patch as
far as 9.2, but I'm disinclined to expend the work until GCC 12
is much more widespread.)

Discussion: https://postgr.es/m/3773792.1645141467@sss.pgh.pa.us

Branch
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REL_14_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/2e30d77a196810f7e9d57709a942b1826fd1bb43

Modified Files
--------------
config/c-compiler.m4 | 22 ++++++++++++++++++++
configure | 40 +++++++++++++++++++++++++++++++++++++
configure.ac | 3 +++
src/backend/postmaster/postmaster.c | 2 +-
src/backend/tcop/postgres.c | 12 ++++++++++-
src/backend/utils/init/miscinit.c | 11 +++++-----
src/include/pg_config.h.in | 3 +++
src/tools/msvc/Solution.pm | 1 +
8 files changed, 86 insertions(+), 8 deletions(-)