`using enum` statements will only be supported by the upcoming Clang 13
compiler, so the current code can't be built with the almost-ready Clang
toolchain yet.
TestProcFs expects to be able to stat its stdout and stderr. The new
ProcFS implemetnation properly forwards the symlinks for
/proc/pid/fd/[1,2] to the temporary file that we had unlinked prior to
spawning the process. However, this makes it so that a normal stat on
the symlink to that file fails (as expected). Move the unlink to after
we've waited on the child, so that we know it won't be trying any funny
business with its stdout/stderr anymore.
This test program heavily pulls from the JavaScriptTestRunner/test-js,
but with a twist. Instead of loading JavaScript files into the current
process, constructing a JS environment for them, and executing test
suites/tests directly, run-tests posix_spawns each test file.
Test file stdout is written to a temp file, and only dumped to console
if the test fails or the verbose option is passed to the program. Unlike
test-js, times are always printed for every test executed for better
visibility in CI.
