Permissions issue when using `CMakePythonPackage` with extensions

[jfgrimm]

When EasyBuild is configured with read-only-installdir, I'm seeing issues like this on a few easyconfigs:

== FAILED: Installation ended unsuccessfully (build directory: /dev/shm/jfg508/pygmo/2.18.0/foss-2022a): build failed (first 300 chars): Failed to copy file /opt/apps/eb/software/EasyBuild/4.8.2/lib/python3.6/site-packages/easybuild/easyblocks/generic/pythonpackage.py to /tmp/eb-niztdg64/reprod_20240108163151_2046843/easyblocks/pythonpackage.py: [Errno 13] Permission denied: '/tmp/eb-niztdg64/reprod_20240108163151_2046843/easyblocks/ (took 1 min 9 secs)

It looks like this only happens for easyconfigs using the CMakePythonPackage easyblock and have extensions. For example:

• pygmo-2.18.0-foss-2022a.eb (CMakePythonPackage + extensions) fails
• EZC3D-1.5.2-foss-2022a.eb (CMakePythonPackage, no extensions) works
• EZC3D-1.5.2-foss-2022a.eb with an arbitrary extension added fails

relevant part from the log with debug output: https://gist.github.com/jfgrimm/b8aa26008bf3da34952c723a9892fa04

[jfgrimm]

I see the same issue with ConfigureMakePythonPackage as well:

== FAILED: Installation ended unsuccessfully (build directory: /dev/shm/jfg508/MUSCLE3/0.7.0/foss-2022b): build failed (first 300 chars): Failed to copy file /opt/apps/eb/software/EasyBuild/4.9.0/lib/python3.6/site-packages/easybuild/easyblocks/generic/pythonpackage.py to /tmp/eb-gfah_z9c/reprod_20240109123220_3468230/easyblocks/pythonpackage.py: [Errno 13] Permission denied: '/tmp/eb-gfah_z9c/reprod_20240109123220_3468230/easyblocks/ (took 1 min 56 secs)