Tests: bsim: update permutations compilation script

The script that compiles different permutations of Kconfig
settings for the control procedures must build each
permutation in sequence. The current implementation of the
compile-script starts each build in the background.

This PR fixes that so that each build now is run sequentially.

Signed-off-by: Andries Kruithof <andries.kruithof@nordicsemi.no>