Currently the build is aborted if the branch tip is at a commit, which
was committed with the email of the 'Eclipse Platform Bot'. This was
done with the intention to prevent (endless) rebuilds after a commit for
a SWT native binary rebuild was pushed by the bot. But because that bot
is also used for other kind of commits, this test leads to false
positives.

An in-depth analysis showed that the pipeline does in fact not get into
an endless native rebuild loop in case that check is removed. Only one
new build is triggered, when a commit for a SWT native binary rebuild is
pushed (as usual for a push), which does not rebuild the native binaries
again, because the latest SWT-native-binary tag points to the then HEAD
commit.
So this reworks the pipeline to just remove that check.

This implicitly also fixes the currently not working check if a native
rebuild is enforced, when testing if the build can be skipped.