opencv: install missing pkgconfig file in staging folder

Signed-off-by: jazzgs <jazzgs@users.noreply.github.com>

libs/opencv/Makefile

@@ -61,6 +61,8 @@ define Build/InstallDev
 	$(CP) $(PKG_INSTALL_DIR)/usr/include/opencv2 $(1)/usr/include/
 	$(INSTALL_DIR) $(1)/usr/lib
 	$(CP) $(PKG_INSTALL_DIR)/usr/lib/libopencv* $(1)/usr/lib/
+	$(INSTALL_DIR) $(1)/usr/lib/pkgconfig
+	$(CP) $(PKG_INSTALL_DIR)/usr/lib/pkgconfig/opencv.pc $(1)/usr/lib/pkgconfig/
 endef
 
 define Package/opencv/install