Use GNUInstallDirs for install destinations

This has the advantage that the user may override e.g. the include
location, and the correct libdir (lib, lib64, lib/something) is
automatically determined.

Closes #1367.

src/CMakeLists.txt

@@ -100,7 +100,7 @@ set_target_properties(glfw PROPERTIES
 target_compile_definitions(glfw PRIVATE _GLFW_USE_CONFIG_H)
 target_include_directories(glfw PUBLIC
                            "$<BUILD_INTERFACE:${GLFW_SOURCE_DIR}/include>"
-                           "$<INSTALL_INTERFACE:$<INSTALL_PREFIX>/include>")
+                           "$<INSTALL_INTERFACE:${CMAKE_INSTALL_FULL_INCLUDEDIR}>")
 target_include_directories(glfw PRIVATE
                            "${GLFW_SOURCE_DIR}/src"
                            "${GLFW_BINARY_DIR}/src"
@@ -121,7 +121,7 @@ target_compile_options(glfw PRIVATE
 if (BUILD_SHARED_LIBS)
     if (WIN32)
         if (MINGW)
-            # Remove the lib prefix on the DLL (but not the import library
+            # Remove the lib prefix on the DLL (but not the import library)
             set_target_properties(glfw PROPERTIES PREFIX "")
 
             # Add a suffix to the import library to avoid naming conflicts
@@ -135,7 +135,7 @@ if (BUILD_SHARED_LIBS)
         target_compile_options(glfw PRIVATE "-fno-common")
 
         set_target_properties(glfw PROPERTIES
-                              INSTALL_NAME_DIR "lib${LIB_SUFFIX}")
+                              INSTALL_NAME_DIR "${CMAKE_INSTALL_LIBDIR}")
     elseif (UNIX)
         # Hide symbols not explicitly tagged for export from the shared library
         target_compile_options(glfw PRIVATE "-fvisibility=hidden")
@@ -155,7 +155,7 @@ if (GLFW_INSTALL)
     install(TARGETS glfw
             EXPORT glfwTargets
             RUNTIME DESTINATION "bin"
-            ARCHIVE DESTINATION "lib${LIB_SUFFIX}"
-            LIBRARY DESTINATION "lib${LIB_SUFFIX}")
+            ARCHIVE DESTINATION "${CMAKE_INSTALL_LIBDIR}"
+            LIBRARY DESTINATION "${CMAKE_INSTALL_LIBDIR}")
 endif()
 

src/glfw3.pc.in

@@ -1,7 +1,7 @@
 prefix=@CMAKE_INSTALL_PREFIX@
 exec_prefix=${prefix}
-includedir=${prefix}/include
-libdir=${exec_prefix}/lib@LIB_SUFFIX@
+includedir=@CMAKE_INSTALL_FULL_INCLUDEDIR@
+libdir=@CMAKE_INSTALL_FULL_LIBDIR@
 
 Name: GLFW
 Description: A multi-platform library for OpenGL, window and input