compileopts: always enable CGo

CGo is needed for the rp2040 and for macOS (GOOS=darwin), without it
these targets just won't work. And there really isn't a benefit from
disabling CGo: we don't need any external linkers for example.

This avoids a somewhat common issue of people having CGO_ENABLED=0
somewhere in their environment and not understanding why things don't
work. See for example: https://github.com/tinygo-org/tinygo/issues/3450

goenv/goenv.go

@@ -142,11 +142,8 @@ func Get(name string) string {
 		}
 		return filepath.Join(dir, "tinygo")
 	case "CGO_ENABLED":
-		val := os.Getenv("CGO_ENABLED")
-		if val == "1" || val == "0" {
-			return val
-		}
-		// Default to enabling CGo.
+		// Always enable CGo. It is required by a number of targets, including
+		// macOS and the rp2040.
 		return "1"
 	case "TINYGOROOT":
 		return sourceDir()