Fix error when HOME is not defined.

The purpose of this is to avoid later Dir.chdir{} calls resulting
in the previous directory being changed to, which may no longer
exist.

This change does not break considering the current directory when running
'portupgrade' or 'portinstall' alone.
Release 2.4.10.4
Add link to ports/175281
Always respect the -O flag to skip sanity checking
Don't run dependency checking with pkgng as pkg.deps has the wrong versions in it.
Merge branch 'master' of github.com:pkgtools/pkgtools
Fix date parsing support with PKGNG

PR:		ports/175926
Merge branch 'master' of github.com:pkgtools/pkgtools