MESA_VK_DEVICE_SELECT_FORCE_DEFAULT_DEVICE=1 is useful but it's tedious to type. This commit extends slightly DRI_PRIME/MESA_VK_DEVICE_SELECT syntax support: if "!" is appended at the end then only the selected GPU will be made visible to the application. Reviewed-by: Adam Jackson <ajax@redhat.com> Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24750>