OndselSolver.pc: support absolute cmake install path

[qbisi]

nixpkgs use absolute CMAKE_INSTALL_* path during cmake configure phase. This pull request remove the need to patch freecad submodule OndselSolver in nixpkgs:
https://github.com/NixOS/nixpkgs/blob/nixos-unstable/pkgs/by-name/fr/freecad/0002-FreeCad-OndselSolver-pkgconfig.patch.

[chennes]

I think you can avoid the branching by using CMake's built-ins, e.g.

set(PKGCONFIG_LIBDIR "${CMAKE_INSTALL_FULL_LIBDIR}")
set(PKGCONFIG_INCLUDEDIR "${CMAKE_INSTALL_FULL_INCLUDEDIR}")

Is OndselSolver.pc being installed?

[qbisi]

I think you can avoid the branching by using CMake's built-ins, e.g.

Thanks, will give it a trial.

Is OndselSolver.pc being installed?

Yes, installed by freecad (nixpkgs have applied a patch to fix the generated OndselSolver.pc )

$ cat /nix/store/42ijx9jg6026846s51rlnxy5dhdi193z-freecad-1.0.2/share/pkgconfig/OndselSolver.pc                         
prefix=/nix/store/42ijx9jg6026846s51rlnxy5dhdi193z-freecad-1.0.2
exec_prefix=/nix/store/42ijx9jg6026846s51rlnxy5dhdi193z-freecad-1.0.2
libdir=${exec_prefix}/lib
includedir=${prefix}/include

Name: OndselSolver
Description: Assembly Constraints and Multibody Dynamics code
Version: 1.0.1

Requires:
Libs: -L${libdir} -lOndselSolver
Cflags: -I${includedir}

[qbisi]

Tested work for me.

[qbisi]

Or just use @CMAKE_INSTALL_FULL_LIBDIR@ @CMAKE_INSTALL_FULL_INCLUDEDIR@ in OndeselSolver.pc.in for simplification ?