cgen: fix runtime sumtype type names on musl

Author: medvednikov

vlib/v/gen/c/cgen.v

@@ -4403,7 +4403,7 @@ fn (mut g Gen) typeof_expr(node ast.TypeOf) {
 	if sym.kind == .sum_type {
 		// When encountering a .sum_type, typeof() should be done at runtime,
 		// because the subtype of the expression may change:
-		g.write('builtin__tos3(v_typeof_sumtype_${sym.cname}( (')
+		g.write('builtin__charptr_vstring_literal(v_typeof_sumtype_${sym.cname}( (')
 		if typ.nr_muls() > 0 {
 			g.write('*'.repeat(typ.nr_muls()))
 		}

vlib/v/gen/c/fn.v

@@ -1692,7 +1692,7 @@ fn (mut g Gen) method_call(node ast.CallExpr) {
 		match node.kind {
 			.type_name {
 				if left_sym.kind in [.sum_type, .interface] {
-					g.conversion_function_call('builtin__tos3(v_typeof_${prefix_name}_${typ_sym.cname}',
+					g.conversion_function_call('builtin__charptr_vstring_literal(v_typeof_${prefix_name}_${typ_sym.cname}',
 						')', node)
 					return
 				}