oeqa/selftest: add test for git working correctly inside pseudo

The fix for CVE-2022-24765 in git[1] breaks any use of git inside
pseudo. Add a simple test case to oe-selftest to verify that at least
basic uses of git work fine under pseudo.

[1] https://github.com/git/git/commit/8959555cee7ec045958f9b6dd62e541affb7e7d9



Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>