add pkgconfig (#3984)

Signed-off-by: sodo <djdisodo@gmail.com>

src/CMakeLists.txt

@@ -513,9 +513,13 @@ if(NCNN_INSTALL_SDK)
     install(EXPORT ncnn DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/ncnn)
     configure_file(${CMAKE_CURRENT_LIST_DIR}/../cmake/ncnnConfig.cmake.in ncnnConfig.cmake @ONLY)
     install(FILES ${CMAKE_CURRENT_BINARY_DIR}/ncnnConfig.cmake DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/ncnn)
+    # pkgconfig
+    configure_file(ncnn.pc.in ${CMAKE_CURRENT_BINARY_DIR}/ncnn.pc @ONLY)
+    install(FILES ${CMAKE_CURRENT_BINARY_DIR}/ncnn.pc DESTINATION ${CMAKE_INSTALL_LIBDIR}/pkgconfig)
 endif()
 
 # add ncnn and generate-spirv to a virtual project group
 set_property(GLOBAL PROPERTY USE_FOLDERS ON)
 set_property(TARGET ncnn PROPERTY FOLDER "libncnn")
 set_property(TARGET ncnn-generate-spirv PROPERTY FOLDER "libncnn")
+

src/ncnn.pc.in

@@ -0,0 +1,11 @@
+prefix=${pcfiledir}/../..
+librarydir=${prefix}/@CMAKE_INSTALL_LIBDIR@
+includedir=${prefix}/@CMAKE_INSTALL_INCLUDEDIR@
+
+Name: @CMAKE_PROJECT_NAME@
+Description: high-performance neural network inference framework optimized for the mobile platform
+Version: @NCNN_VERSION_STRING@
+URL: https://github.com/Tencent/ncnn
+Libs: -L"${librarydir}" -lncnn
+Cflags: -I"${includedir}"
+