cmake: Enable pkgconfig support for mingw

CMakeLists.txt

@@ -641,7 +641,7 @@ ocv_cmake_hook(POST_COMPILER_OPTIONS)
 # ----------------------------------------------------------------------------
 #       CHECK FOR SYSTEM LIBRARIES, OPTIONS, ETC..
 # ----------------------------------------------------------------------------
-if(UNIX)
+if(UNIX OR MINGW)
   if(NOT APPLE_FRAMEWORK OR OPENCV_ENABLE_PKG_CONFIG)
     if(CMAKE_CROSSCOMPILING AND NOT DEFINED ENV{PKG_CONFIG_LIBDIR} AND NOT DEFINED ENV{PKG_CONFIG_SYSROOT_DIR}
         AND NOT OPENCV_ENABLE_PKG_CONFIG
@@ -673,6 +673,8 @@ if(UNIX)
       # no need to link to system libs with emscripten
     elseif(QNXNTO)
       set(OPENCV_LINKER_LIBS ${OPENCV_LINKER_LIBS} m)
+    elseif(MINGW)
+      set(OPENCV_LINKER_LIBS ${OPENCV_LINKER_LIBS} pthread)
     else()
       set(OPENCV_LINKER_LIBS ${OPENCV_LINKER_LIBS} dl m pthread rt)
     endif()

cmake/OpenCVGenPkgconfig.cmake

@@ -103,7 +103,7 @@ add_custom_target(gen-pkgconfig ALL SOURCES "${CMAKE_BINARY_DIR}/unix-install/${
 add_dependencies(developer_scripts gen-pkgconfig)
 
 
-if(UNIX AND NOT ANDROID)
+if((UNIX AND NOT ANDROID) OR MINGW)
   install(FILES ${CMAKE_BINARY_DIR}/unix-install/${OPENCV_PC_FILE_NAME} DESTINATION ${OPENCV_LIB_INSTALL_PATH}/pkgconfig COMPONENT dev)
 endif()