This patch solves the following issues:
- The pkg-config files generates odd paths when using DESTDIR without PREFIX
- DESTDIR is needed during compile time to compute library and header paths which it should not.
- Installing with both DESTDIR and PREFIX set gives us odd paths
- Make usage of DESTDIR and PREFIX more standard
Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>
ln on macOS doesn't support --relative, so use the gnu version by default.
Also document how to build on macOS.
Signed-off-by: Karl MacMillan <karlwmacmillan@gmail.com>