refactor: test for intel oneapi env vars

[wpbonelli]

This PR introduces a check for the SETVARS_COMPLETED environment variable before running Intel oneAPI setvars scripts. This variable is set to 1 by Intel oneAPI scripts to indicate that the oneAPI environment has been configured. This can prevent path length errors on Windows caused by repeatedly running setvars scripts in the same session.

Here is a passing integration test run with install-intelfortran-action which uses my fork of pymake with this change.

[codecov[bot]]

Codecov Report

Merging #125 (39398b8) into master (2519822) will increase coverage by 0.097%. The diff coverage is 100.000%.

@@              Coverage Diff              @@
##            master      #125       +/-   ##
=============================================
+ Coverage   62.500%   62.597%   +0.097%     
=============================================
  Files           17        17               
  Lines         4480      4481        +1     
=============================================
+ Hits          2800      2805        +5     
+ Misses        1680      1676        -4     

Impacted Files	Coverage Δ
pymake/pymake_base.py	86.743% <100.000%> (+0.017%)	:arrow_up:
pymake/utils/download.py	69.428% <0.000%> (+1.142%)	:arrow_up: