CMake: generate SkUserConfig.h with configure_file

cmake/CMakeLists.txt

 # Boilerplate.
 cmake_minimum_required (VERSION 3.1)   # First version with CMAKE_CXX_STANDARD.
 project (skimake)
 set (CMAKE_CXX_STANDARD 11)
 
 # Default to Release mode.  We're mainly targeting Skia users, not Skia developers.
 if (NOT CMAKE_BUILD_TYPE)
     set (CMAKE_BUILD_TYPE Release)
 endif ()
 
@@ skipping 198 matching lines @@
 
 if (APPLE)
     find_library(APPLICATION_SERVICES_FRAMEWORK ApplicationServices REQUIRED)
     list (APPEND libs ${APPLICATION_SERVICES_FRAMEWORK})
 endif()
 
 if (OSMESA_LIBRARIES AND OSMESA_INCLUDE_DIRS)
     list (APPEND libs             ${OSMESA_LIBRARIES})
     list (APPEND private_includes ${OSMESA_INCLUDE_DIRS})
     list (APPEND public_defines   "-DSK_MESA=1")
+    set (SK_MESA 1)
 else()
     remove_srcs(../src/gpu/gl/mesa/*)
 endif()
 
 if (WIN32)
     list (APPEND libs FontSub.lib Usp10.lib)
 endif()
 
 find_package(OpenGL REQUIRED)
 list (APPEND libs  ${OPENGL_LIBRARIES})
@@ skipping 25 matching lines @@
     COMPILE_FLAGS ${cc_flags}
     CXX_VISIBILITY_PRESET hidden
     VISIBILITY_INLINES_HIDDEN true)
 
 # Experimental C API install:
 file(GLOB c_headers "../include/c/*.h")
 install(FILES ${c_headers} DESTINATION include)
 install(TARGETS skia DESTINATION lib)
 
 # SkUserConfig.h
-set (userconfig_path ${userconfig_directory}/SkUserConfig.h)
-file(WRITE ${userconfig_path} "// SkUserConfig generated by CMake.\n")
-file(APPEND ${userconfig_path} "#ifndef SkUserConfig_DEFINED\n")
-file(APPEND ${userconfig_path} "#define SkUserConfig_DEFINED\n")
 if (CMAKE_BUILD_TYPE STREQUAL Release)
-  file(APPEND ${userconfig_path} "#define SK_RELEASE\n")
-  file(APPEND ${userconfig_path} "#undef SK_DEBUG\n")
-else ()
-  file(APPEND ${userconfig_path} "#define SK_DEBUG\n")
-  file(APPEND ${userconfig_path} "#undef SK_RELEASE\n")
-endif ()
-if (OSMESA_LIBRARIES AND OSMESA_INCLUDE_DIRS)
-  file (APPEND ${userconfig_path} "#define SK_MESA 1\n")
+    set (SK_RELEASE 1)
 endif()
-file(APPEND ${userconfig_path} "#endif  // SkUserConfig_DEFINED\n")
+configure_file ("SkUserConfig.h.in" "${userconfig_directory}/SkUserConfig.h")
 
 # skia_link_arguments.txt
 set (link_arguments ${CMAKE_BINARY_DIR}/skia_link_arguments.txt)
 file (WRITE ${link_arguments} "-L${CMAKE_BINARY_DIR}\n")
 file (APPEND ${link_arguments} "-lskia\n")
 file (APPEND ${link_arguments} "-Wl,-rpath,${CMAKE_BINARY_DIR}\n")
 
 # skia_compile_arguments.txt
 set (compile_arguments ${CMAKE_BINARY_DIR}/skia_compile_arguments.txt)
 file (WRITE ${compile_arguments} "--std=c++11\n")
@@ skipping 24 matching lines @@
         file (APPEND ${skia_h_path} "#include \"${filename_component}\"\n")
       endif ()
     endforeach()
   endif()
 endforeach()
 file(APPEND ${skia_h_path} "\n#endif  // skia_DEFINED\n")
 
 # Now build a simple example app that uses Skia via libskia.so.
 add_executable(example example.cpp)
 target_link_libraries(example skia ${OPENGL_LIBRARIES})