initramfs_build: Update with the actual script being run

The buildroot-master initramfs build job was using a version of this
script from https://github.com/csmart/openbmc-build-scripts.git#endianess

Change-Id: I702656c7f2738bc928959eed7a280b2d78edf2ba
Signed-off-by: Joel Stanley <joel@jms.id.au>
1 file changed