misc/dist: don't ship cmd/cov or cmd/prof

Fixes #3317

R=golang-dev, dsymonds
CC=golang-dev
https://golang.org/cl/5784083

misc/dist/bindist.go

@@ -43,6 +43,8 @@ const (
 )
 
 var preBuildCleanFiles = []string{
+	"src/cmd/cov",
+	"src/cmd/prof",
 	"src/pkg/exp",
 	"src/pkg/old",
 }

src/cmd/dist/build.c

@@ -1214,6 +1214,8 @@ clean(void)
 	vinit(&dir);
 
 	for(i=0; i<nelem(cleantab); i++) {
+		if((streq(cleantab[i], "cmd/cov") || streq(cleantab[i], "cmd/prof")) && !isdir(cleantab[i]))
+			continue;
 		bpathf(&path, "%s/src/%s", goroot, cleantab[i]);
 		xreaddir(&dir, bstr(&path));
 		// Remove generated files.