Revert "Removed unused configuration option"

This reverts commit 74b2d526d7.

Makefile.am

@@ -81,6 +81,18 @@ EXTRA_DIST += \
 	data/swupd-update.timer \
 	data/verifytime.service
 
+DISTCHECK_CONFIGURE_FLAGS = \
+	--with-systemdsystemunitdir=$$dc_install_base/$(systemdunitdir)
+
+systemdunitdir = @SYSTEMD_UNITDIR@
+
+systemdunit_DATA = \
+	data/check-update.service \
+	data/check-update.timer \
+	data/swupd-update.service \
+	data/swupd-update.timer \
+	data/verifytime.service
+
 distclean-local:
 	rm -rf aclocal.m4 ar-lib autom4te.cache config.guess config.h.in config.h.in~ config.sub configure depcomp install-sh ltmain.sh m4 Makefile.in missing compile
 

configure.ac

@@ -240,6 +240,18 @@ AS_IF(
     AC_MSG_ERROR(['--with-formatid' has an invalid value ($with_formatid). Supported values are positive integers or "staging".])]
 )
 
+AC_ARG_WITH(
+  [systemdsystemunitdir],
+  [AS_HELP_STRING([--with-systemdsystemunitdir=DIR], [path to systemd system service dir @<:@default=/usr/lib/systemd/system@:>@])],
+  [unitpath=${withval}],
+  [unitpath="$($PKG_CONFIG --variable=systemdsystemunitdir systemd)"]
+)
+AS_IF(
+  [test -z "${unitpath}"],
+  [unitpath=/usr/lib/systemd/system]
+)
+AC_SUBST(SYSTEMD_UNITDIR, [${unitpath}])
+
 AC_ARG_WITH(
   [pre-update],
   [AS_HELP_STRING([--with-pre-update=EXE], [Path to the pre-update executable])],