Fix --with-systemd on Debian-based distributions (#6963)

These changes propagate the "--with-systemd" configure option to the
RPM spec file, allowing Debian-based distributions to package
systemd-related files.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: loli10K <ezomori.nozomu@gmail.com>
Closes #6591 
Closes #6963

config/user-systemd.m4

@@ -2,7 +2,8 @@ AC_DEFUN([ZFS_AC_CONFIG_USER_SYSTEMD], [
 	AC_ARG_ENABLE(systemd,
 		AC_HELP_STRING([--enable-systemd],
 		[install systemd unit/preset files [[default: yes]]]),
-		[],enable_systemd=yes)
+		[enable_systemd=$enableval],
+		[enable_systemd=check])
 
 	AC_ARG_WITH(systemdunitdir,
 		AC_HELP_STRING([--with-systemdunitdir=DIR],
@@ -19,16 +20,27 @@ AC_DEFUN([ZFS_AC_CONFIG_USER_SYSTEMD], [
 		[install systemd module load files into dir [[/usr/lib/modules-load.d]]]),
 		systemdmoduleloaddir=$withval,systemdmodulesloaddir=/usr/lib/modules-load.d)
 
+	AS_IF([test "x$enable_systemd" = xcheck], [
+		AS_IF([systemctl --version >/dev/null 2>&1],
+			[enable_systemd=yes],
+			[enable_systemd=no])
+	])
 
-	AS_IF([test "x$enable_systemd" = xyes],
-		[
+	AC_MSG_CHECKING(for systemd support)
+	AC_MSG_RESULT([$enable_systemd])
+
+	AS_IF([test "x$enable_systemd" = xyes], [
 		ZFS_INIT_SYSTEMD=systemd
 		ZFS_MODULE_LOAD=modules-load.d
+		DEFINE_SYSTEMD='--with systemd --define "_unitdir $(systemdunitdir)" --define "_presetdir $(systemdpresetdir)"'
 		modulesloaddir=$systemdmodulesloaddir
-		])
+	],[
+		DEFINE_SYSTEMD='--without systemd'
+	])
 
 	AC_SUBST(ZFS_INIT_SYSTEMD)
 	AC_SUBST(ZFS_MODULE_LOAD)
+	AC_SUBST(DEFINE_SYSTEMD)
 	AC_SUBST(systemdunitdir)
 	AC_SUBST(systemdpresetdir)
 	AC_SUBST(modulesloaddir)

config/zfs-build.m4

@@ -160,7 +160,7 @@ AC_DEFUN([ZFS_AC_RPM], [
 	])
 
 	RPM_DEFINE_COMMON='--define "$(DEBUG_ZFS) 1"'
-	RPM_DEFINE_UTIL='--define "_dracutdir $(dracutdir)" --define "_udevdir $(udevdir)" --define "_udevruledir $(udevruledir)" --define "_initconfdir $(DEFAULT_INITCONF_DIR)" $(DEFINE_INITRAMFS)'
+	RPM_DEFINE_UTIL='--define "_dracutdir $(dracutdir)" --define "_udevdir $(udevdir)" --define "_udevruledir $(udevruledir)" --define "_initconfdir $(DEFAULT_INITCONF_DIR)" $(DEFINE_INITRAMFS) $(DEFINE_SYSTEMD)'
 	RPM_DEFINE_KMOD='--define "kernels $(LINUX_VERSION)" --define "require_spldir $(SPL)" --define "require_splobj $(SPL_OBJ)" --define "ksrc $(LINUX)" --define "kobj $(LINUX_OBJ)"'
 	RPM_DEFINE_DKMS=
 

rpm/generic/zfs.spec.in

@@ -88,12 +88,15 @@ BuildRequires:  libudev-devel
 BuildRequires:  libattr-devel
 BuildRequires:  openssl-devel
 Requires:       openssl
+%if 0%{?_systemd}
+BuildRequires: systemd
+%endif
 %endif
+
 %if 0%{?_systemd}
 Requires(post): systemd
 Requires(preun): systemd
 Requires(postun): systemd
-BuildRequires: systemd
 %endif
 
 # The zpool iostat/status -c scripts call some utilities like lsblk and iostat