makefile: install scripts to bin instead of sbin

sbin isn't usr merge compliant, and it should have no functional impact by having it in bin

Makefile

 install:
 	install -Dm 755 src/swclock-offset-boot.sh \
-		$(DESTDIR)$(PREFIX)/sbin/swclock-offset-boot
+		$(DESTDIR)$(PREFIX)/bin/swclock-offset-boot
 	install -Dm 755 src/swclock-offset-shutdown.sh \
-		$(DESTDIR)$(PREFIX)/sbin/swclock-offset-shutdown
+		$(DESTDIR)$(PREFIX)/bin/swclock-offset-shutdown
 
 install_openrc:
 	install -Dm 755 openrc/swclock-offset-boot.initd \