Makefile shell constructs are not POSIX-compliant

[mhucka]

Describe the issue

There are Bash-isms in the top-level Makefile, and these turn out to fail on some Linux systems.

Tell us how to reproduce the issue

Running make on a fairly stock GCP Ubuntu VM results in errors about the shell script fragment for check-cuquantum-root-set.

Tell us the version of qsim or qsimcirq (if relevant)

No response

Tell us the computing environment (if relevant)

No response

[mhucka]

Fixed in PR #879.