replace run_cmd with run_shell_cmd in custom easyblock for ESMF (esmf.py)

[branfosj]

(created using eb --new-pr)

• No use of EB_ESMF in easyconfigs or blocks

[branfosj]

Test report by @branfosj

Overview of tested easyconfigs (in order)

• SUCCESS netCDF-C++4-4.3.1-gompi-2022a.eb
• SUCCESS ESMF-8.4.2-foss-2022a.eb

Build succeeded for 2 out of 2 (1 easyconfigs in total)
bear-pg0105u03a - Linux RHEL 8.6, x86_64, Intel(R) Xeon(R) Platinum 8360Y CPU @ 2.40GHz (icelake), Python 3.6.8
See https://gist.github.com/branfosj/3a862b8ce60cd4344a89a12362a5b1d6 for a full test report.