pgsql: meson: Move C99 test earlier

meson: Move C99 test earlier

Move the test for compiler options for C99 earlier in meson.build,
before we make use of the compiler for other tests. That way, if any
command-line options are needed, subsequent tests will also use them.
This is at the moment a theoretical problem, but it seems better to
get this correct. It also matches the order in the Autoconf-based
build more closely.

Discussion: /messages/by-id/01a69441-af54-4822-891b-ca28e05b215a@eisentraut.org

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/4a4038068bb29eff2516296fc842b88741625afd

Modified Files
--------------
meson.build | 85 ++++++++++++++++++++++++++++++-------------------------------
1 file changed, 42 insertions(+), 43 deletions(-)