common: Support a gpgconf.ctl file under Unix.

* common/homedir.c (unix_rootdir): New.
(gnupg_bindir): Use it.
(gnupg_libexecdir): Use it.
(gnupg_libdir): Use it.
(gnupg_datadir): Use it.
(gnupg_localedir): Use it.
--

This feature is useful for building and using an AppImage version of
gnupg and probably also for some other use cases.

GnuPG-bug-id: 5999

Here is a sample gpgconf.ctl file
--8<---------------cut here---------------start------------->8---
# gpgconf.ctl
#
# This file is used to change the directories where the gpg components
# are installed.  It does not change the configuration directories.
# The file is expected in the same directory as gpgconf.  The physical
# installation directories are evaluated and no symlinks.  Blank lines
# and lines starting with pound signed are ignored.  No errors are
# printed for unknown keywords or commands.  The only defined key for
# now is "rootdir" which must be followed by one optional space, an
# equal sign, and the value for the root directory.  Environment
# variables are substituted in standard shell manner, the final value
# must start with a slash, trailing slashed are stripped.

rootdir = $APPDIR/gnupg
--8<---------------cut here---------------end--------------->8---

0 files changed, 0 insertions, 0 deletions