compiler: predeclare runtime.trackPointer

When a package only uses runtime.trackPointer to create interface packs, the compiler fails to find runtime.trackPointer.
This change predeclares it alongside runtime.alloc and updates the tests to use runtime.trackPointer when the test's target uses it.

compiler/compiler_test.go

@@ -109,6 +109,7 @@ func TestCompiler(t *testing.T) {
 				FuncImplementation: config.FuncImplementation(),
 				AutomaticStackSize: config.AutomaticStackSize(),
 				DefaultStackSize:   config.Target.DefaultStackSize,
+				NeedsStackObjects:  config.NeedsStackObjects(),
 			}
 			machine, err := NewTargetMachine(compilerConfig)
 			if err != nil {