meson: Add support for detecting gss without pkg-config
This is required as MIT Kerberos does provide neither pkg-config nor cmake
dependency information on windows.
Reported-by: Dave Page <dpage@pgadmin.org>
Reviewed-by: Tristan Partin <tristan@partin.io>
Discussion: https://postgr.es/m/
20240709065101.xhc74r3mdg2lmn4w@awork3.anarazel.de
Backpatch: 16-, where meson support was added