cmd/dist, cmd/go: pass -fmessage-length always

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/36300044

src/cmd/dist/build.c

@@ -677,9 +677,9 @@ install(char *dir)
 			vadd(&gccargs, "-fno-caret-diagnostics");
 			// clang is too smart about unused command-line arguments
 			vadd(&gccargs, "-Qunused-arguments");
-			// disable line wrapping in error messages
-			vadd(&gccargs, "-fmessage-length=0");
 		}
+		// disable word wrapping in error messages
+		vadd(&gccargs, "-fmessage-length=0");
 		if(streq(gohostos, "darwin")) {
 			// golang.org/issue/5261
 			vadd(&gccargs, "-mmacosx-version-min=10.6");

src/cmd/go/build.go

@@ -1890,10 +1890,11 @@ func (b *builder) ccompilerCmd(envvar, defcmd, objdir string) []string {
 		a = append(a, "-fno-caret-diagnostics")
 		// clang is too smart about command-line arguments
 		a = append(a, "-Qunused-arguments")
-		// disable word wrapping in error messages
-		a = append(a, "-fmessage-length=0")
 	}
 
+	// disable word wrapping in error messages
+	a = append(a, "-fmessage-length=0")
+
 	// On OS X, some of the compilers behave as if -fno-common
 	// is always set, and the Mach-O linker in 6l/8l assumes this.
 	// See http://golang.org/issue/3253.