abuild: Stop polluting/conflicting in the startdir
Currently, in the start directory, two temporary directories are created, 'pkg' and 'src'. While these directories are reasonable in their name, they also invite for clashes and just pollute the namespace.
While this does not have to be a problem strictly for official aports, users writing their own, out of tree, aports may get bitten by this.
Instead, lets avoid name-clashing and polluting with temporary directories by moving them into the '.abuild' subdirectory instead.
Signed-off-by: Olliver Schinagl email@example.com