configure.ac: manually expand PKG_CHECK_VAR

The macro is introduced with pkgconfig v0.28 which isn't universally
available. Thus it will error at configure stage.

Reported-by: Brian Paul <brianp@vmware.com>
Tested-by: Brian Paul <brianp@vmware.com>
Fixes: ce562f9e3fa ("EGL: Implement the libglvnd interface for EGL (v3)")
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
1 file changed