Use whereis to find setcap install location and cut to trim the output

<Dan_C> DigitalMan: minor install issue noted today - during a fresh (Linux) install on a test box, the build failed because it was unable to execute the "sudo setcap ..." command.  This was on Slackware 15.0, where the setcap executable is located in /sbin , and that directory is not in the $PATH of a normal user, or even when a normal user uses the 'sudo' command.

src/sbbs3/targets.mk

@@ -133,7 +133,7 @@ endif
 ifeq ($(os),linux)
 .PHONY: setcap
 setcap: all
-	sudo setcap 'cap_net_bind_service=+ep' $(EXEODIR)/sbbs
+	sudo $(whereis -b setcap | cut -d" " -f2) 'cap_net_bind_service=+ep' $(EXEODIR)/sbbs
 endif
 
 .PHONY: sexyz