runqemu: fixes for when invoked during a bitbake run
When runqemu is invoked from a running bitbake instance it will be
unable to call `bitbake -e` due to the lock held by the calling
bitbake instance.
Our test code sets an OE_TMPDIR environment variable from which we
can infer/guess paths. Add code to do so when self.bitbake_e can't
be set, much as the sh version of runqemu did.
[YOCTO #10240]
Signed-off-by: Joshua Lock <joshua.g.lock@intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
