bugfix: avoid spack race condition #173

Job	Run time
changa_netlrts-linux-x86_64	6m 4s
buildold_netlrts-linux-x86_64	17m 24s
cuda_netlrts-linux-x86_64_buildonly	12m 5s
charm4py_netlrts-linux-x86_64_tcp	5m 54s
mpi-linux-x86_64_syncft	10m 18s
namd_netlrts-linux-x86_64	11m 54s
multicore-darwin-x86_64_projections	1s
netlrts-darwin-x86_64	1s
doc	40s
netlrts-linux-i386	16m 38s
netlrts-linux-x86_64	15m 15s
mpi-linux-x86_64	13m 3s
netlrts-linux-x86_64_smp	22m 4s
netlrts-linux-x86_64_syncft	10m 10s
netlrts-win-x86_64_mingw64	18m 6s
spack_ubuntu-latest	26m 20s
shellcheck	5s
spack_macos-12	1s
ucx-linux-x86_64_openpmix	16m 3s
verbs-linux-x86_64_smp	13m 38s
	3h 35m 44s

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