configure: correctly report if we're building the sw/xlib winsys

While looking at bug 75356, I've noticed that the presence of
x11 egl platform pulls in sw/xlib as "needed" but fails to
report so at the end of configure.

Tested-by: Tom Stellard <thomas.stellard@amd.com>
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
1 file changed