patch(1) has a -d/--directory parameter which allows us to specify a directory
where the patch will be applied. This is especially useful when we have
multiple distfiles and want to patch in $build_wrksrc because that's where the
patch is usually applied.
Problem is, that the -i parameter is also relative to the the -d parameter and
thus fails to find the patch, when -d is set. We solve that by using standard
input instead of -i.
The -l option causes a looser behavior of patch(1), where patches
are applied when there is a match with no regard to leading
whitespace. This means that it is possible to get false positives:
for example, in srcpkgs/glu, there is a patch that was supposed
to be long gone (since the release already includes it) but it
was overlooked since with -l it happens to apply in a different
portion of the source (where it is wrong).
Avoid these cases.
