Use GNUInstallDirs for install targets

Distributions like Fedora use /usr/lib64 for their 64bit versions and termcolor
has hardcoded /usr/lib install path. By using `GNUInstallDirs` automatically
can be detected which path should be used.

CMakeLists.txt

@@ -10,7 +10,7 @@ add_library(${PROJECT_NAME}::${PROJECT_NAME} ALIAS ${PROJECT_NAME})
 
 target_include_directories(${PROJECT_NAME} INTERFACE
   $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
-  $<INSTALL_INTERFACE:include>)
+  $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>)
 target_compile_features(${PROJECT_NAME} INTERFACE cxx_std_11)
 
 #
@@ -31,25 +31,28 @@ endif()
 
 include(CMakePackageConfigHelpers)
 
+# Installation paths
+include(GNUInstallDirs)
+
 configure_package_config_file(
   cmake/config.cmake.in
   ${CMAKE_CURRENT_BINARY_DIR}/generated/${PROJECT_NAME}-config.cmake
-  INSTALL_DESTINATION lib/cmake/${PROJECT_NAME})
+  INSTALL_DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME})
 
 install(
   FILES ${CMAKE_CURRENT_BINARY_DIR}/generated/${PROJECT_NAME}-config.cmake
-  DESTINATION lib/cmake/${PROJECT_NAME})
+  DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME})
 
 install(
   DIRECTORY include/
-  DESTINATION include)
+  DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
 
 install(
   TARGETS ${PROJECT_NAME}
   EXPORT ${PROJECT_NAME}-targets
-  INCLUDES DESTINATION include)
+  INCLUDES DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
 
 install(
   EXPORT ${PROJECT_NAME}-targets
   NAMESPACE ${PROJECT_NAME}::
-  DESTINATION lib/cmake/${PROJECT_NAME})
+  DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME})