cli: clarify runtime.alloc linker error with -gc=none

This should help people figure out the actual problem if they run into
this.

builder/tools.go

@@ -121,9 +121,11 @@ func parseLLDErrors(text string) error {
 				if matches != nil {
 					parsedError = true
 					line, _ := strconv.Atoi(matches[3])
-					// TODO: detect common mistakes like -gc=none?
 					msg := "linker could not find symbol " + symbolName
-					if symbolName == "runtime.alloc_noheap" {
+					switch symbolName {
+					case "runtime.alloc":
+						msg = "object allocated on the heap with -gc=none"
+					case "runtime.alloc_noheap":
 						msg = "object allocated on the heap in //go:noheap function"
 					}
 					linkErrors = append(linkErrors, scanner.Error{