FreeBSD build failure: HAVE_SECURE_GETENV erroneously set for openxr dependency

[phryk]

Godot version

4.0.dev (040f49e)

System information

FreeBSD 13.1-RELEASE, GENERIC kernel, amd64

Issue description

When specifying the linuxbsd platform for scons during build, modules/openxr/SCsub
defines HAVE_SECURE_GETENV for the openxr third-party dependency. This define
implies the existence of the function secure_getenv – which FreeBSD doesn't have.

That in turn leads to the build currently failing on FreeBSD when it encounters this:

#ifdef HAVE_SECURE_GETENV
    return secure_getenv(name);

I can confirm that commenting out the define of HAVE_SECURE_GETENV in
modules/openxr/SCsub fixes said build failure on FreeBSD, but am not too
sure how to fix this without finally introducing BSD as its own platform.

I also can't speak on whether the other BSDs provide secure_getenv,
but a cursory check for corresponding man pages on man.openbsd.org
and man.netbsd.org yields no results.

Steps to reproduce

• Run scons platform=linuxbsd on FreeBSD

Minimal reproduction project

No response