mesa: enable building without distro feature x11
mesa: enable building without distro feature x11

No packageconfig for 'gl' will be created if not building glx, (when
removing x11 from distro features), but some of the postprocessing
steps assume it will be there.

This change simply checks if gl.pc exists before trying to fix it
up.

Signed-off-by: Kurt Kiefer <33e41f3cd91d2553c4528f8892b4c2d945b05381@gmail.com>
Signed-off-by: Matt Madison <1fa2ef4755a9226cb9a0a4840bd89b158ac71391@madison.systems>

madisongh/meta-tegra,madisongh/meta-tegra,madisongh/meta-tegra,madisongh/meta-tegra,madisongh/meta-tegra