fix(main/opencv): install pkg-config script as well

It is considered deprecated and not installed by opencv per default.

Partially fixes https://github.com/termux/termux-packages/issues/10886.

packages/opencv/build.sh

@@ -15,6 +15,7 @@ TERMUX_PKG_EXTRA_CONFIGURE_ARGS="
 -DWITH_OPENEXR=OFF
 -DBUILD_PROTOBUF=OFF
 -DPROTOBUF_UPDATE_FILES=ON
+-DOPENCV_GENERATE_PKGCONFIG=ON
 "
 
 termux_step_post_get_source() {