package/llvm: bump to version 9.0.1
Go back to the github url download again.
See:
http://lists.llvm.org/pipermail/llvm-announce/2019-December/000086.html
Cc: Joseph Kogut <joseph.kogut@gmail.com>
Cc: Valentin Korenblit <valentinkorenblit@gmail.com>
Signed-off-by: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>