build: Add -c and --cmd as aliases for --task

This aligns us with bitbake. Moreover, -c/--cmd is easier to tell apart
from --target. Keep --task for backward compatibility.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

kas/build.py

@@ -62,7 +62,7 @@ class Build:
         bld_psr.add_argument('--target',
                              action='append',
                              help='Select target to build')
-        bld_psr.add_argument('--task',
+        bld_psr.add_argument('-c', '--cmd', '--task',
                              help='Select which task should be executed')
         bld_psr.add_argument('--skip',
                              help='Skip build steps',