classes/buildhistory: record removals in buildhistory directory

classes/buildhistory: record removals in buildhistory directory

"git add ." does not record files that were removed in the buildhistory
directory. Specify the -A flag to also record removals.

This was discovered by the following warning added in Git 1.8.3:
warning: You ran 'git add' with neither '-A (--all)' or '--ignore-removal',
whose behaviour will change in Git 2.0 with respect to paths you removed.

(From OE-Core rev: a45a247e2cfa58892a0c9eb050d603a38cd839db)

Signed-off-by: Jonathan Liu <net147@gmail.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>