Fix IDE errors with unresolved R.* symbols.

[no ci]

shell-loader/build.gradle

@@ -1,7 +1,7 @@
 //file:noinspection UnnecessaryQualifiedReference, GrDeprecatedAPIUsage
 apply plugin: 'com.android.application'
 
-android.namespace 'com.termux.x11'
+android.namespace 'com.termux.x11.shell_loader'
 android.defaultConfig.minSdkVersion 21
 android.compileSdkVersion 28
 android.buildTypes.debug.signingConfig null

shell-loader/src/main/java/com/termux/x11/Loader.java

@@ -1,4 +1,5 @@
 package com.termux.x11;
+import com.termux.x11.shell_loader.BuildConfig;
 
 public class Loader {
     /**

shell-loader/stub/build.gradle

@@ -3,7 +3,7 @@ plugins {
 }
 
 android {
-    namespace 'com.termux.x11'
+    namespace 'com.termux.x11.stub'
     compileSdkVersion 30
     defaultConfig {
         minSdkVersion 24