games-emulation/RetroArch: add desktop database update

[BakedSnake]

 * QA Notice: .desktop files with MimeType= were found installed
 * but desktop mimeinfo cache has not been updated:
 *   /usr/share/applications/com.libretro.RetroArch.desktop
 * Please make sure to call xdg_desktop_database_update()
 * in pkg_postinst() and pkg_postrm() phases of appropriate pkgs.

Closes: https://bugs.gentoo.org/975056

the second commit addresses a dependency issue:
https://github.com/raspberrypi/userland
Apparently this is now ancient and deprecated. Some of the tools have been moved to raspberrypi-utils.

The few useful tools from here (dtoverlay, dtmerge, vcmailbox, vcgencmd) have been moved to the raspberrypi/utils repo.

pkgcheck scan --net ... is clean.

Regards
-Gil

[BakedSnake]

It is also worth mentioning that both media-libs/raspberrypi-userland and media-libs/raspberrypi-userland-bin are not present in guru anymore.

games-emulation/RetroArch
  NonexistentDeps: version 1.22.2: DEPEND: nonexistent packages: media-libs/raspberrypi-userland-bin:0, media-libs/raspberrypi-userland:0
  NonexistentDeps: version 1.22.2: RDEPEND: nonexistent packages: media-libs/raspberrypi-userland-bin:0, media-libs/raspberrypi-userland:0