cmake: Provide a pkgconfig file (#83)

Fixes #80

Signed-off-by: Andreas Schneider <asn@cryptomilk.org>

CMakeLists.txt

@@ -318,6 +318,8 @@ if(AVIF_BUILD_TESTS)
     )
 endif()
 
+configure_file(libavif.pc.cmake ${CMAKE_CURRENT_BINARY_DIR}/libavif.pc @ONLY)
+
 if(NOT SKIP_INSTALL_LIBRARIES AND NOT SKIP_INSTALL_ALL)
     install(TARGETS avif
         EXPORT ${PROJECT_NAME}-config
@@ -336,6 +338,9 @@ if(NOT SKIP_INSTALL_LIBRARIES AND NOT SKIP_INSTALL_ALL)
         install(FILES ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}-config-version.cmake
                 DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME})
     endif()
+
+    install(FILES ${CMAKE_CURRENT_BINARY_DIR}/libavif.pc
+            DESTINATION ${CMAKE_INSTALL_LIBDIR}/pkgconfig)
 endif()
 if(NOT SKIP_INSTALL_HEADERS AND NOT SKIP_INSTALL_ALL)
     install(FILES include/avif/avif.h

libavif.pc.cmake

@@ -0,0 +1,10 @@
+prefix=@CMAKE_INSTALL_FULL_PREFIX@
+exec_prefix=${prefix}/bin
+libdir=${prefix}/lib
+includedir=${prefix}/include
+
+Name: @PROJECT_NAME@
+Description: Library for encoding and decoding .avif files
+Version: @PROJECT_VERSION@
+Libs: -L${libdir} -lavif
+Cflags: -I{includedir}