Make resulting cmake config relocatable

This change avoids hardcoded install prefix in the p8-platform-config.cmake.
Especially important when doing cross compilation with Yocto for example.

Author: bachp

CMakeLists.txt

@@ -22,10 +22,6 @@ if(WIN32)
                    src/windows/os-threads.cpp)
 endif()
 
-set(p8-platform_INCLUDE_DIRS "${CMAKE_INSTALL_PREFIX}/include/p8-platform")
-IF(WIN32)
-  LIST(APPEND p8-platform_INCLUDE_DIRS "${CMAKE_INSTALL_PREFIX}/include/p8-platform/windows")
-ENDIF(WIN32)
 set(p8-platform_LIBRARIES ${CMAKE_THREAD_LIBS_INIT})
 
 if(NOT ${CORE_SYSTEM_NAME} STREQUAL "")

p8-platform-config.cmake.in

@@ -9,17 +9,22 @@
 #  p8-platform_LIBRARY_DIRS - directories in which the libraries are situated
 #
 # propagate these properties from one build system to the other
+get_filename_component(_p8-platform_rootdir ${CMAKE_CURRENT_LIST_DIR}/../ ABSOLUTE)
+
 set (p8-platform_VERSION "@p8-platform_VERSION_MAJOR@.@p8-platform_VERSION_MINOR@")
-set (p8-platform_INCLUDE_DIRS @p8-platform_INCLUDE_DIRS@ @CMAKE_INSTALL_PREFIX@/include)
-set (p8-platform_LIBRARY_DIRS "@CMAKE_LIBRARY_OUTPUT_DIRECTORY@")
+set (p8-platform_INCLUDE_DIRS "${_p8-platform_rootdir}/include" "${_p8-platform_rootdir}/include/p8-platform")
+if(WIN32)
+  list(APPEND p8-platform_INCLUDE_DIRS "${_p8-platform_rootdir}/include/p8-platform/windows")
+endif(WIN32)
+set (p8-platform_LIBRARY_DIRS "${_p8-platform_rootdir}")
 set (p8-platform_LINKER_FLAGS "@p8-platform_LINKER_FLAGS@")
 set (p8-platform_CONFIG_VARS "@p8-platform_CONFIG_VARS@")
 
 # libraries come from the build tree where this file was generated
 if(WIN32)
-  set (p8-platform_LIBRARY "@CMAKE_INSTALL_PREFIX@/@CMAKE_INSTALL_LIBDIR@/p8-platform.lib")
+  set (p8-platform_LIBRARY "${_p8-platform_rootdir}/p8-platform.lib")
 else(WIN32)
-  set (p8-platform_LIBRARY "-L@CMAKE_INSTALL_PREFIX@/@CMAKE_INSTALL_LIBDIR@ -lp8-platform")
+  set (p8-platform_LIBRARY "-L${_p8-platform_rootdir} -lp8-platform")
 endif(WIN32)
 set (p8-platform_LIBRARIES ${p8-platform_LIBRARY} "@p8-platform_LIBRARIES@")
 mark_as_advanced (p8-platform_LIBRARY)