package_manager.py: Allow a leading - in PACKAGE_EXCLUDE_COMPLEMENTARY

package_manager.py: Allow a leading - in PACKAGE_EXCLUDE_COMPLEMENTARY

This allows a regular expression specified in
PACKAGE_EXCLUDE_COMPLEMENTARY to have a leading dash. Without this,
the dash was treated by oe-pkgdata-util as the beginning of a command
line argument. E.g., if PACKAGE_EXCLUDE_COMPLEMENTARY = "-foo$", it
resulted in an error like:

  ERROR: <imagename>-1.0-r0 do_populate_sdk: Could not compute
  complementary packages list. Command '<topdir>/scripts/oe-pkgdata-util -p
  <builddir>/tmp/sysroots/<machine>/pkgdata glob
  <workdir>/installed_pkgs.txt *-dev *-dbg -x -foo$' returned 2:
  ERROR: argument -x/--exclude: expected one argument
  usage: oe-pkgdata-util glob [-h] [-x EXCLUDE] pkglistfile glob [glob ...]

(From OE-Core rev: ac4ca41d3a27356d46c0c39053e74d3519b24c44)

Signed-off-by: Peter Kjellerstedt <peter.kjellerstedt@axis.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>