This was needed since we had to have a way for the test suites to override this value. However,
this can also be acheived by writing to configure/CONFIG_CELL.local. This was added in a
refactoring of run_make to make more clear what variables can be passed there.

E3-286: refactor tests

See merge request e3/e3-require!74

E3-610: Set STREAM_PROTOCOL_PATH

See merge request e3/e3-require!75

Note that any module that depends on StreamDevice will load it first using `handleDependencies` which
is called before we add the _DB paths. So if a module depends on StreamDevice, this will be accurately
caught; moreover, if StreamDevice is not loaded, then we don't bother setting this path.

e3-577: remove base v3

See merge request e3/e3-require!72

E3-669: Formatting

See merge request e3/e3-require!71

Remove special mode-file

See merge request e3/e3-require!70

Fix CI

See merge request e3/e3-require!69

Apply pre-commit

See merge request e3/e3-require!68

E3-665: Add tests for KEEP_HEADER_SUBDIRS

See merge request e3/e3-require!67