all: add linux/mipsle support

This adds linux/mipsle (little endian Mips) support to TinyGo.

It also adds experimental linux/mips (big-endian) support. It doesn't
quite work yet, some parts of the standard library (like the reflect
package) currently seem to assume a little-endian system.

compileopts/config.go

@@ -212,7 +212,10 @@ func (c *Config) RP2040BootPatch() bool {
 func MuslArchitecture(triple string) string {
 	arch := strings.Split(triple, "-")[0]
 	if strings.HasPrefix(arch, "arm") || strings.HasPrefix(arch, "thumb") {
-		arch = "arm"
+		return "arm"
+	}
+	if arch == "mipsel" {
+		return "mips"
 	}
 	return arch
 }