Enable / Disable iOS support depending on xcode-select

Summary:
Queries xcode-select on ios dispatcher startup, to see if it's installed.
If it is, carry on with the ios device tracking, if not, don't bother.

This should stop it from emitting errors trying to track devices when things aren't installed.

I think it should also stop those install prompts from popping up.

Sets it in app state so we can tell the user about it, and maybe gate some other things too.

Reviewed By: passy

Differential Revision: D17830696

fbshipit-source-id: 960d09a9c5267afabf5e5e222379a0a7ed2cc444

src/reducers/application.tsx

@@ -76,6 +76,7 @@ export type State = {
   launcherMsg: LauncherMsg;
   flipperRating: number | null;
   statusMessages: Array<string>;
+  xcodeCommandLineToolsDetected: boolean;
 };
 
 type BooleanActionType =
@@ -140,6 +141,12 @@ export type Action =
   | {
       type: 'REMOVE_STATUS_MSG';
       payload: {msg: string; sender: string};
+    }
+  | {
+      type: 'SET_XCODE_DETECTED';
+      payload: {
+        isDetected: boolean;
+      };
     };
 
 export const initialState: () => State = () => ({
@@ -161,6 +168,7 @@ export const initialState: () => State = () => ({
   },
   flipperRating: null,
   statusMessages: [],
+  xcodeCommandLineToolsDetected: false,
 });
 
 function statusMessage(sender: string, msg: string): string {
@@ -268,6 +276,8 @@ export default function reducer(
       return {...state, statusMessages};
     }
     return state;
+  } else if (action.type === 'SET_XCODE_DETECTED') {
+    return {...state, xcodeCommandLineToolsDetected: action.payload.isDetected};
   } else {
     return state;
   }
@@ -345,3 +355,8 @@ export const removeStatusMessage = (payload: StatusMessageType): Action => ({
   type: 'REMOVE_STATUS_MSG',
   payload,
 });
+
+export const setXcodeDetected = (isDetected: boolean): Action => ({
+  type: 'SET_XCODE_DETECTED',
+  payload: {isDetected},
+});