- need the udunits-2 package
 - need a 'personal access token' for github

see:
  https://dynverse.org/users/1-installation/
  https://www.unidata.ucar.edu/software/udunits/
  https://github.com/

The implicit --no-environ of the --vanilla option would
inhibit the evaluation of the GITHUB_PAT variable

Bonus: MAKEFLAGS are now evaluated too, speeding up the
       package builds by approx. 50%

Control the number of threads on 'BLAS' (Aka 'GotoBLAS',
'OpenBLAS', 'ACML', 'BLIS' and 'MKL'). And possible to
control the number of threads in 'OpenMP'. Get a number
of logical cores and physical cores if feasible.

Sounded good to me...
Only works if an external BLAS is used, not the one
that's bundled with R

Environment vars from root are not seen by the build
user, so a simple export GITHUB_PAT=... before the
build won't work.