graphics/gstreamer1-plugins-gl: Prevent fetch during build

If git(1) was found on the system, the port would attempt to download
OpenGL headers for a meson subproject from [1], which seems to only be
necessary/intended for Windows. Add '--wrap-mode=nodownload' to
MESON_ARGS to prevent this behavior. This only affects builds on live
systems.

While here: Remove unused glu dep from USE_GL and add jpeg dep as this
will link to libjpeg if found on the system. Tiny Makefile order fix.

[1] https://gitlab.freedesktop.org/gstreamer/meson-ports/gl-headers

PR: 270184
Reported by: amdmi3