Make packages installation dirs in global octave_packages file relative to OCTAVE_HOME (bug #51632). * make_rel_paths.m, expand_rel_paths.m: New files that replace OCTAVE_HOME part of packages installation path with __OH__, or vice versa. * pkg.m, install.m, uninstall.m: Call make_rel_paths.m before saving octave_packages file. * installed_packages.m: Add call to expand_rel_paths.m and standardize_paths.m. * module.mk: Add expand_rel_path.m and make_rel_path.m.

--- a/scripts/pkg/pkg.m	Sun Nov 17 11:39:57 2019 +0100
+++ b/scripts/pkg/pkg.m	Sat Nov 16 23:32:42 2019 +0100
@@ -567,6 +567,7 @@
           ## On Windows ensure LFN paths are saved rather than 8.3 style paths
           global_packages = standardize_paths (global_packages);
         endif
+        global_packages = make_rel_paths (global_packages);
         save (global_list, "global_packages");
         if (nargout)
           local_packages = global_packages;