Let CMake figure out pkgconfig directories

Author: doronbehar

CMakeLists.txt

@@ -156,8 +156,6 @@ install(EXPORT ${PROJECT_NAME}-targets
         FILE ${PROJECT_NAME}Targets.cmake
         DESTINATION ${XSIMD_CMAKECONFIG_INSTALL_DIR})
 
-join_paths(libdir_for_pc_file "\${exec_prefix}" "${CMAKE_INSTALL_LIBDIR}")
-join_paths(includedir_for_pc_file "\${prefix}" "${CMAKE_INSTALL_INCLUDEDIR}")
 configure_file(${PROJECT_NAME}.pc.in
                "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}.pc"
                 @ONLY)

xsimd.pc.in

@@ -1,6 +1,6 @@
 prefix=@CMAKE_INSTALL_PREFIX@
-libdir=@libdir_for_pc_file@
-includedir=@includedir_for_pc_file@
+libdir=@CMAKE_INSTALL_FULL_LIBDIR@
+includedir=@CMAKE_INSTALL_FULL_INCLUDEDIR@
 
 Name: xsimd
 Description: xsimd provides a unified means for using SIMD features for library authors..