Environment vars must be defined on top-level, otherwise running
`abuild rootpkg` separately produces different results.

py3-numpy is built against OpenBLAS that also provides optimized LAPACK.
See 9f56f959.

This reverts commit 285190d0.

mips is dead, completely dead.

This reverts part of commit 7c305355.

openblas is available again

limited by openblas

fixes commit f75e8d98 (community/py3-numpy: upgrade to 1.20.1)