Use char const * in oc_popen.

[1uc]

This silences an warning related to oc_popen(..., "r").

[azure-pipelines]

✔️ 5a92341 -> Azure artifacts URL

[codecov]

Codecov Report

Merging #2532 (5a92341) into master (b4fdb4c) will decrease coverage by 0.01%.
Report is 10 commits behind head on master.
The diff coverage is n/a.

❗ Current head 5a92341 differs from pull request most recent head 2364fa5. Consider uploading reports for the commit 2364fa5 to get more accurate results

@@            Coverage Diff             @@
##           master    #2532      +/-   ##
==========================================
- Coverage   61.48%   61.48%   -0.01%     
==========================================
  Files         623      623              
  Lines      119146   119152       +6     
==========================================
  Hits        73261    73261              
- Misses      45885    45891       +6     

Files	Coverage Δ
src/oc/fileio.cpp	80.80% <ø> (ø)

... and 4 files with indirect coverage changes

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more

[azure-pipelines]

✔️ 5a92341 -> Azure artifacts URL

[bbpbuildbot]

Logfiles from GitLab pipeline #156471 (:white_check_mark:) have been uploaded here!

Status and direct links:

• ✅ mac_m1_cmake_build: [cmake, ON, OFF, OFF, address]
• ✅ spack_setup
• ✅ build:nmodl
• ✅ build:neuron:nmodl:intel:legacy
• ✅ build:neuron:nmodl:intel:shared
• ✅ build:neuron:nmodl:nvhpc:acc:legacy
• ✅ build:neuron:nmodl:nvhpc:acc:shared
• ✅ build:neuron:nmodl:nvhpc:omp:legacy
• ✅ build:neuron:nmodl:nvhpc:omp
• ✅ test:neuron:nmodl:intel:legacy
• ✅ test:neuron:nmodl:intel:shared
• ✅ test:neuron:nmodl:nvhpc:acc:legacy
• ✅ test:neuron:nmodl:nvhpc:acc:shared
• ✅ test:neuron:nmodl:nvhpc:omp:legacy
• ✅ test:neuron:nmodl:nvhpc:omp