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

compileopts/config.go

@@ -87,12 +87,6 @@ func (c *Config) BuildTags() []string {
 	return tags
 }
 
-// CgoEnabled returns true if (and only if) CGo is enabled. It is true by
-// default and false if CGO_ENABLED is set to "0".
-func (c *Config) CgoEnabled() bool {
-	return goenv.Get("CGO_ENABLED") == "1"
-}
-
 // GC returns the garbage collection strategy in use on this platform. Valid
 // values are "none", "leaking", "conservative" and "precise".
 func (c *Config) GC() string {