compiler: correctly generate code for local named types

It is possible to create function-local named types:

    func foo() any {
        type named int
        return named(0)
    }

This patch makes sure they don't alias with named types declared at the
package scope.

Bug originally found by Damian Gryski while working on reflect support.

compiler/func.go

@@ -32,7 +32,8 @@ func (c *compilerContext) createFuncValue(builder llvm.Builder, funcPtr, context
 // global reference is not real, it is only used during func lowering to assign
 // signature types to functions and will then be removed.
 func (c *compilerContext) getFuncSignatureID(sig *types.Signature) llvm.Value {
-	sigGlobalName := "reflect/types.funcid:" + getTypeCodeName(sig)
+	s, _ := getTypeCodeName(sig)
+	sigGlobalName := "reflect/types.funcid:" + s
 	sigGlobal := c.mod.NamedGlobal(sigGlobalName)
 	if sigGlobal.IsNil() {
 		sigGlobal = llvm.AddGlobal(c.mod, c.ctx.Int8Type(), sigGlobalName)