Clean build of IDE fails on macOS

[mwu-tow]

Currently

./run ide build

will fail on macOS, even if all requirements are met.

This is side-effect of #8351 which introduced adding GraalPy's python to PATH. The GraalPy is then picked up by electron-builder and fails the packaging process. Apparently, GraalPy still is not compatible with CPython.

This appeared following the merge of #9884 which removed workarounds that located python2 and forced electron-builder to use it.

Probably the Engine setup should be changed to not modify PATH globally, but only for the spawned Engine-building processes.

---

The issue can be worked around by running ./run ide build with any option preventing the engine from being built — e.g. --backend-release nightly or --backend-source local.

---

Originally reported on Discord.