build-sys: allow skipping installation of completions

./configure --with-bashcompletiondir=no or --without-bashcompletiondir
now works as expected. Similarly for zsh.

https://github.com/systemd/systemd/issues/533

Makefile.am

@@ -414,6 +414,7 @@ systemgenerator_PROGRAMS = \
 	systemd-system-update-generator \
 	systemd-debug-generator
 
+if ENABLE_BASH_COMPLETION
 dist_bashcompletion_DATA = \
 	shell-completion/bash/busctl \
 	shell-completion/bash/journalctl \
@@ -430,7 +431,9 @@ dist_bashcompletion_DATA = \
 
 nodist_bashcompletion_DATA = \
 	shell-completion/bash/systemctl
+endif
 
+if ENABLE_ZSH_COMPLETION
 dist_zshcompletion_DATA = \
 	shell-completion/zsh/_busctl \
 	shell-completion/zsh/_journalctl \
@@ -447,6 +450,7 @@ dist_zshcompletion_DATA = \
 
 nodist_zshcompletion_DATA = \
 	shell-completion/zsh/_systemctl
+endif
 
 EXTRA_DIST += \
 	shell-completion/bash/systemctl.in \
@@ -2228,8 +2232,10 @@ SYSINIT_TARGET_WANTS += \
 	systemd-tmpfiles-setup-dev.service \
 	systemd-tmpfiles-setup.service
 
+if ENABLE_ZSH_COMPLETION
 dist_zshcompletion_DATA += \
 	shell-completion/zsh/_systemd-tmpfiles
+endif
 
 TIMERS_TARGET_WANTS += \
 	systemd-tmpfiles-clean.timer
@@ -2460,12 +2466,16 @@ bootctl_LDADD = \
 bin_PROGRAMS += \
 	bootctl
 
+if ENABLE_BASH_COMPLETION
 dist_bashcompletion_DATA += \
 	shell-completion/bash/bootctl
+endif
 
+if ENABLE_ZSH_COMPLETION
 dist_zshcompletion_DATA += \
 	shell-completion/zsh/_bootctl
 endif
+endif
 
 # ------------------------------------------------------------------------------
 if HAVE_GNUEFI
@@ -4247,11 +4257,15 @@ test_coredump_vacuum_SOURCES = \
 test_coredump_vacuum_LDADD = \
 	libshared.la
 
+if ENABLE_BASH_COMPLETION
 dist_bashcompletion_DATA += \
 	shell-completion/bash/coredumpctl
+endif
 
+if ENABLE_ZSH_COMPLETION
 dist_zshcompletion_DATA += \
 	shell-completion/zsh/_coredumpctl
+endif
 
 nodist_sysctl_DATA = \
 	sysctl.d/50-coredump.conf
@@ -4499,12 +4513,15 @@ hostnamectl_LDADD = \
 bin_PROGRAMS += \
 	hostnamectl
 
+if ENABLE_BASH_COMPLETION
 dist_bashcompletion_DATA += \
 	shell-completion/bash/hostnamectl
+endif
 
+if ENABLE_ZSH_COMPLETION
 dist_zshcompletion_DATA += \
 	shell-completion/zsh/_hostnamectl
-
+endif
 endif
 
 polkitpolicy_in_files += \
@@ -4570,12 +4587,15 @@ localectl_LDADD = \
 bin_PROGRAMS += \
 	localectl
 
+if ENABLE_BASH_COMPLETION
 dist_bashcompletion_DATA += \
 	shell-completion/bash/localectl
+endif
 
+if ENABLE_ZSH_COMPLETION
 dist_zshcompletion_DATA += \
 	shell-completion/zsh/_localectl
-
+endif
 endif
 
 .PHONY: update-kbd-model-map
@@ -4627,12 +4647,16 @@ timedatectl_LDADD = \
 bin_PROGRAMS += \
 	timedatectl
 
+if ENABLE_BASH_COMPLETION
 dist_bashcompletion_DATA += \
 	shell-completion/bash/timedatectl
+endif
 
+if ENABLE_ZSH_COMPLETION
 dist_zshcompletion_DATA += \
 	shell-completion/zsh/_timedatectl
 endif
+endif
 
 polkitpolicy_in_files += \
 	src/timedate/org.freedesktop.timedate1.policy.in
@@ -4738,8 +4762,10 @@ machinectl_LDADD = \
 rootbin_PROGRAMS += \
 	machinectl
 
+if ENABLE_BASH_COMPLETION
 dist_bashcompletion_DATA += \
 	shell-completion/bash/machinectl
+endif
 
 test_machine_tables_SOURCES = \
 	src/machine/test-machine-tables.c
@@ -4768,9 +4794,11 @@ dist_dbuspolicy_DATA += \
 polkitpolicy_files += \
 	src/machine/org.freedesktop.machine1.policy
 
+if ENABLE_ZSH_COMPLETION
 dist_zshcompletion_DATA += \
 	shell-completion/zsh/_machinectl \
 	shell-completion/zsh/_sd_machines
+endif
 
 SYSTEM_UNIT_ALIASES += \
 	systemd-machined.service dbus-org.freedesktop.machine1.service
@@ -5330,12 +5358,16 @@ loginctl_LDADD = \
 rootbin_PROGRAMS += \
 	loginctl
 
+if ENABLE_BASH_COMPLETION
 dist_bashcompletion_DATA += \
 	shell-completion/bash/loginctl
+endif
 
+if ENABLE_ZSH_COMPLETION
 dist_zshcompletion_DATA += \
 	shell-completion/zsh/_loginctl \
 	shell-completion/zsh/_systemd-inhibit
+endif
 
 systemd_inhibit_SOURCES = \
 	src/login/inhibit.c

configure.ac

@@ -1340,11 +1340,13 @@ AC_ARG_WITH([bashcompletiondir],
         ] , [
                 with_bashcompletiondir=${datadir}/bash-completion/completions
         ])])
+AM_CONDITIONAL(ENABLE_BASH_COMPLETION, [test "$with_bashcompletiondir" != "no"])
 AX_NORMALIZE_PATH([with_bashcompletiondir])
 
 AC_ARG_WITH([zshcompletiondir],
         AS_HELP_STRING([--with-zshcompletiondir=DIR], [Zsh completions directory]),
         [], [with_zshcompletiondir=${datadir}/zsh/site-functions])
+AM_CONDITIONAL(ENABLE_ZSH_COMPLETION, [test "$with_zshcompletiondir" != "no"])
 AX_NORMALIZE_PATH([with_zshcompletiondir])
 
 AC_ARG_WITH([rootprefix],