when lsof cannot be found in PATH, search in /usr/local/bin, /usr/bin…

…, /bin, /usr/sbin and /sbin

this helps using tmux as a default shell on macOS where PATH is initially set to /usr/bin:/bin

resolves gpakosz#587

.tmux.conf

@@ -145,7 +145,7 @@ bind P choose-buffer    # choose which buffer to paste from
 # -- 8< ------------------------------------------------------------------------
 
 %if #{==:#{TMUX_PROGRAM},}
-  run 'TMUX_PROGRAM="$(lsof -b -w -a -d txt -p #{pid} -Fn 2>/dev/null | perl -n -e "if (s/^n((?:.(?!dylib$|so$))+)$/\1/g) { print; exit } } exit 1; {" || readlink "/proc/#{pid}/exe" 2>/dev/null || printf tmux)"; "$TMUX_PROGRAM" -S #{socket_path} set-environment -g TMUX_PROGRAM "$TMUX_PROGRAM"'
+  run 'TMUX_PROGRAM="$(LSOF=$(PATH="$PATH:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin" command -v lsof); $LSOF -b -w -a -d txt -p #{pid} -Fn 2>/dev/null | perl -n -e "if (s/^n((?:.(?!dylib$|so$))+)$/\1/g) { print; exit } } exit 1; {" || readlink "/proc/#{pid}/exe" 2>/dev/null || printf tmux)"; "$TMUX_PROGRAM" -S #{socket_path} set-environment -g TMUX_PROGRAM "$TMUX_PROGRAM"'
 %endif
 %if #{==:#{TMUX_SOCKET},}
   run '"$TMUX_PROGRAM" -S #{socket_path} set-environment -g TMUX_SOCKET "#{socket_path}"'