added make target "run" to compile & run gnuradio-companion flowchart

Makefile

@@ -1,2 +1,6 @@
 BOARD_TAG = uno
 include /usr/share/arduino/Arduino.mk
+
+# https://www.gnu.org/software/make/manual/html_node/Automatic-Variables.html
+run: scope.grc
+	grcc --run $^