Wolfgang reported over in [1] that I've missed a comma when appending to the PKG_CONFIG_REQUIRES_PRIVATE list, making libpq.pc look ugly:
Requires.private: libssl, libcrypto libcurl
pkg-config itself appears to be papering over my mistake (a quick code inspection suggests it treats commas as equivalent to whitespace?) but here's a patch to fix it. I went with a macro inspired by Makefile.global's add_to_path, to try to ease this for whoever comes next.
LGTM
Tested with GNU Make 3.81 (the compilation of which was slightly painful; does anyone want to debate pulling that minimum version up sometime soon?) and 4.3.
Not sure if all animals have a minimum 4.3 make version. Do you?