Cwd under miniperl (at this point) can't determine the current
directory if some ancestor directory isn't readable.
So Cwd::getcwd() would return undef, and write_buildcustomize.pl
would write out a list of paths relative to / rather than to the cwd.
my $cwd = Cwd::getcwd();
+defined $cwd
+ or die "$0: Can't determine current working directory\n";
+
# lib must be last, as the toolchain modules write themselves into it
# as they build, and it's important that @INC order ensures that the partially
# written files are always masked by the complete versions.