texlive: fix cross

[dkwo]

• I tested the changes in this PR: native
• I have no way of testing crossbuilt binaries, until they are built on Void's builders.
• I built this PR locally for these architectures (aarch64-glibc)

[leahneukirchen]

Need to remove nocross= ;)

[leahneukirchen]

I think testing cross builds aarch64 -> armv7{,-musl} etc locally should be possible.

There are weird LuaJIT errors I couldn't fix within 10min.

[dkwo]

I made luajit option nocross, since it is tricky to crosscompile: we should use system one when that becomes available.
Also web2c requires small tricks for cross, which could be upstreamed.