Unbreak build on FreeBSD
CC @manu. Makes the following succeed:
$ meson -Dudev_kms=false _build
$ ninja -C _build
Clang < 9 also bumps into the following I didn't bother to fix:
../test/xtest.c:64:23: error: suggest braces around initialization of subobject [-Werror,-Wmissing-braces]
WindowRec root = {0};
^
{}