Teach abuild to emit JUnit formatted build reports

Teach abuild to emit JUnit formatted build reports

Jenkins can produce reports from JUnit test cases, so we fake testcases
for each board.

Change-Id: I34d46d15c83f4f04d2228f302eb626b261ac098d
Reviewed-on: http://review.coreboot.org/1
Tested-by: build bot (Jenkins)
Reviewed-by: Sven Schnelle <svens@stackframe.org>
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>