long option --parents doesn't work for old versions of mkdir. It appears short...

long option --parents doesn't work for old versions of mkdir. It appears short option -p does. So fixed that.

RIGAL/rigsc.446/src/Makefile

@@ -44,7 +44,7 @@ normal:   bins ../lib/riglib.a ../bin/anrig ../bin/genrigd ../bin/rig_lint test
 
 bins:     bin ../bin/rc ../bin/ic ../bin/v
 bin:
-	-mkdir --parents ../bin
+	-mkdir -p ../bin
 
 #rigal_scratch:#
 #	rm -rf ../rigal_scratch