build: Support meson-0.49.2

Ternary operator inside method call crashes the parser,
so it's relocated outside.

This change will help to build project under latest debian:10

Forwarded: https://gitlab.freedesktop.org/glvnd/libglvnd/-/merge_requests
Bug: https://github.com/NVIDIA/libglvnd/issues/198
Relate-to: https://github.com/mesonbuild/meson/issues/5003
Signed-off-by: Philippe Coval <rzr@users.sf.net>
Change-Id: I18b6e8eca7564a6a252fff1ec6299311a3a92669
12 jobs for sandbox/rzr/review/master in 3 minutes and 33 seconds (queued for 1 second)