support -extldflags

Fixes #4320

compileopts/config.go

@@ -395,6 +395,16 @@ func (c *Config) LDFlags() []string {
 	if c.Target.LinkerScript != "" {
 		ldflags = append(ldflags, "-T", c.Target.LinkerScript)
 	}
+
+	if c.Options.ExtLDFlags != "" {
+		ext, err := shlex.Split(c.Options.ExtLDFlags)
+		if err != nil {
+			// if shlex can't split it, pass it as-is and let the external linker complain
+			ext = []string{c.Options.ExtLDFlags}
+		}
+		ldflags = append(ldflags, ext...)
+	}
+
 	return ldflags
 }
 

compileopts/options.go

@@ -56,6 +56,7 @@ type Options struct {
 	Timeout         time.Duration
 	WITPackage      string // pass through to wasm-tools component embed invocation
 	WITWorld        string // pass through to wasm-tools component embed -w option
+	ExtLDFlags      string
 }
 
 // Verify performs a validation on the given options, raising an error if options are not valid.

main.go

@@ -1388,6 +1388,7 @@ func main() {
 	cpuprofile := flag.String("cpuprofile", "", "cpuprofile output")
 	monitor := flag.Bool("monitor", false, "enable serial monitor")
 	baudrate := flag.Int("baudrate", 115200, "baudrate of serial monitor")
+	extLDFlags := flag.String("extldflags", "", "additional flags to pass to external linker")
 
 	// Internal flags, that are only intended for TinyGo development.
 	printIR := flag.Bool("internal-printir", false, "print LLVM IR")
@@ -1503,6 +1504,7 @@ func main() {
 		Timeout:         *timeout,
 		WITPackage:      witPackage,
 		WITWorld:        witWorld,
+		ExtLDFlags:      *extLDFlags,
 	}
 	if *printCommands {
 		options.PrintCommands = printCommand