main: add -debug flag that controls debuginfo stripping

Debug information is useful in many case, but in the case of WebAssembly
it increases the binary size by a large amount. It also inhibits
compression of relocations. Therefore I've made debug information
optional and disabled by default.

(Debug information is still generated, but stripped from the binary at
the link step).

main.go

@@ -1019,6 +1019,7 @@ func main() {
 	printStacks := flag.Bool("print-stacks", false, "print stack sizes of goroutines")
 	printAllocsString := flag.String("print-allocs", "", "regular expression of functions for which heap allocations should be printed")
 	printCommands := flag.Bool("x", false, "Print commands")
+	debug := flag.String("debug", "auto", "remove debug information (auto, true, false)")
 	nodebug := flag.Bool("no-debug", false, "disable DWARF debug symbol generation")
 	ocdCommandsString := flag.String("ocd-commands", "", "OpenOCD commands, overriding target spec (can specify multiple separated by commas)")
 	ocdOutput := flag.Bool("ocd-output", false, "print OCD daemon output during debug")
@@ -1086,7 +1087,8 @@ func main() {
 		PrintIR:         *printIR,
 		DumpSSA:         *dumpSSA,
 		VerifyIR:        *verifyIR,
-		Debug:           !*nodebug,
+		EmitDWARF:       !*nodebug,
+		Debug:           *debug,
 		PrintSizes:      *printSize,
 		PrintStacks:     *printStacks,
 		PrintAllocs:     printAllocs,
@@ -1173,7 +1175,7 @@ func main() {
 			err := Flash(pkgName, *port, options)
 			handleCompilerError(err)
 		} else {
-			if !options.Debug {
+			if !options.EmitDWARF {
 				fmt.Fprintln(os.Stderr, "Debug disabled while running gdb?")
 				usage()
 				os.Exit(1)