cpupower: make systemd unit installation optional

cpupower currently installs a cpupower.service unit file into unitdir
unconditionally, regardless of whether systemd is used by the host.

Improve the installation procedure by making this systemd step optional:
a 'SYSTEMD' build parameter that defaults to 'true' and can be set to
'false' to disable the installation of systemd's unit file.

Since 'SYSTEMD' defaults to true, the current behavior is kept as the
default.

Link: https://lore.kernel.org/r/20260113132753.1730020-2-joaomarcos.costa@bootlin.com
Signed-off-by: João Marcos Costa <joaomarcos.costa@bootlin.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

Author: jmarcoscosta

tools/power/cpupower/Makefile

@@ -315,7 +315,17 @@ endif
 	$(INSTALL_DATA) lib/cpuidle.h $(DESTDIR)${includedir}/cpuidle.h
 	$(INSTALL_DATA) lib/powercap.h $(DESTDIR)${includedir}/powercap.h
 
-install-tools: $(OUTPUT)cpupower
+# SYSTEMD=false disables installation of the systemd unit file
+SYSTEMD ?=	true
+
+install-systemd:
+	$(INSTALL) -d $(DESTDIR)${unitdir}
+	sed 's|___CDIR___|${confdir}|; s|___LDIR___|${libexecdir}|' cpupower.service.in > '$(DESTDIR)${unitdir}/cpupower.service'
+	$(SETPERM_DATA) '$(DESTDIR)${unitdir}/cpupower.service'
+
+INSTALL_SYSTEMD := $(if $(filter true,$(strip $(SYSTEMD))),install-systemd)
+
+install-tools: $(OUTPUT)cpupower $(INSTALL_SYSTEMD)
 	$(INSTALL) -d $(DESTDIR)${bindir}
 	$(INSTALL_PROGRAM) $(OUTPUT)cpupower $(DESTDIR)${bindir}
 	$(INSTALL) -d $(DESTDIR)${bash_completion_dir}
@@ -324,9 +334,6 @@ install-tools: $(OUTPUT)cpupower
 	$(INSTALL_DATA) cpupower-service.conf '$(DESTDIR)${confdir}'
 	$(INSTALL) -d $(DESTDIR)${libexecdir}
 	$(INSTALL_PROGRAM) cpupower.sh '$(DESTDIR)${libexecdir}/cpupower'
-	$(INSTALL) -d $(DESTDIR)${unitdir}
-	sed 's|___CDIR___|${confdir}|; s|___LDIR___|${libexecdir}|' cpupower.service.in > '$(DESTDIR)${unitdir}/cpupower.service'
-	$(SETPERM_DATA) '$(DESTDIR)${unitdir}/cpupower.service'
 
 install-man:
 	$(INSTALL_DATA) -D man/cpupower.1 $(DESTDIR)${mandir}/man1/cpupower.1
@@ -406,4 +413,4 @@ help:
 	@echo  '  uninstall	  - Remove previously installed files from the dir defined by "DESTDIR"'
 	@echo  '                    cmdline or Makefile config block option (default: "")'
 
-.PHONY: all utils libcpupower update-po create-gmo install-lib install-tools install-man install-gmo install uninstall clean help
+.PHONY: all utils libcpupower update-po create-gmo install-lib install-systemd install-tools install-man install-gmo install uninstall clean help