maskRootdir() built its strip-regex from this process's os.tmpdir(), so it
only masked paths whose root matched the current tmpdir. That is fragile in
two real cases:
- The path being masked is recorded when the compile runs and need not
share the masking process's tmpdir. Snapshots/fixtures that freeze
/tmp/... paths only mask on hosts where os.tmpdir() is /tmp (they fail
where it is e.g. /usr/tmp).
- On macOS os.tmpdir() returns /var/folders/... while real temp paths
often resolve via /private/var/folders/..., so masking silently missed.
- A configured temp root (temp dirs created outside os.tmpdir()) was never
matched at all.
Key the regex off the distinctive ce_temp_prefix marker instead, matching
whatever path segments precede it. This is tmpdir-independent and unifies the
Windows and non-Windows branches into one rule (also masking embedded temp
paths like `-I/tmp/.../include` on Windows, which the old anchored branch
missed).
Adds unit tests for maskRootdir (previously untested) covering /tmp,
/usr/tmp, macOS /private/var, Windows, the -I include case, and non-temp
paths left untouched.
c86dafabe2