cmd/cc, cmd/gc: set ctxt->debugvlog with debug['v']

LGTM=rsc
R=rsc, iant
CC=golang-codereviews
https://golang.org/cl/118610043

src/cmd/cc/lex.c

@@ -203,6 +203,7 @@ main(int argc, char *argv[])
 	
 	flagparse(&argc, &argv, usage);
 	ctxt->debugasm = debug['S'];
+	ctxt->debugvlog = debug['v'];
 
 	if(argc < 1 && outfile == 0)
 		usage();

src/cmd/gc/lex.c

@@ -319,6 +319,7 @@ main(int argc, char *argv[])
 
 	flagparse(&argc, &argv, usage);
 	ctxt->debugasm = debug['S'];
+	ctxt->debugvlog = debug['v'];
 
 	if(argc < 1)
 		usage();