Makefile: specify SHAREDIR as a default-if-not-specified variable.

Makefile

@@ -7,7 +7,7 @@ DESTDIR ?=
 PREFIX ?= /usr/local
 ETCDIR=/etc/x2go
 LIBDIR ?= $(PREFIX)/lib/x2go
-SHAREDIR=$(PREFIX)/share/x2go
+SHAREDIR ?= $(PREFIX)/share/x2go
 
 PERL ?= /usr/bin/perl
 PERL_INSTALLDIRS ?= vendor

debian/changelog

@@ -97,6 +97,7 @@ x2goserver (4.1.0.4-0x2go1.1) UNRELEASED; urgency=medium
     - x2goserver/bin/x2gopath.in: hardcode LIBDIR, PREFIX and SHAREDIR at
       build time, but also allow re-rooting afterwards - derived from the
       original values.
+    - Makefile: specify SHAREDIR as a default-if-not-specified variable.
   * debian/control:
     + Build-depend upon lsb-release for distro version detection.
   * debian/x2goserver.manpages: