The executable version probe added in ecb22957 ("validate Linux browser
executables") replaced the file-only check in resolveSystemChromium with
isChromiumExecutable, which spawns the candidate `--version` for every
platform. On Windows chrome.exe is a GUI-subsystem binary: `--version`
does not print to a detached stdout and can hand off to a running
instance, opening/activating the user's normal browser window, after
which the probe rejects the candidate and falls back to cached Chrome
for Testing.
Gate the spawn probe on process.platform === "linux" (its intended
platform, where non-Chromium PATH wrappers are the real risk) and trust
the executable-file check on Windows and macOS.
Fixes#8445
roboomp
cf1ff14f5f