Android: Add a dependency on the AndroidX appcompat library.

It's apache licensed so it's ok, and I need it for some Storage Access
Framework work for #11997.

android/AndroidManifest.xml

@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:tools="http://schemas.android.com/tools"
     package="org.ppsspp.ppsspp"
     android:installLocation="auto"
     android:versionCode="111020000"
@@ -28,6 +29,9 @@
     <uses-permission-sdk-23 android:name="android.permission.CAMERA" />
     <uses-permission-sdk-23 android:name="android.permission.RECORD_AUDIO" />
 
+	<!-- AndroidX minimum SDK workaround. We don't care if it's broken on older versions. -->
+	<uses-sdk tools:overrideLibrary="androidx.appcompat.resources,androidx.appcompat,androidx.fragment,androidx.drawerlayout,androidx.vectordrawable.animated,androidx.vectordrawable,androidx.viewpager,androidx.loader,androidx.activity,androidx.annotation,androidx.customview,androidx.cursoradapter,androidx.arch,androidx.collection,androidx.core,androidx.versionedparcelable,androidx.interpolator,androidx.lifecycle,androidx.loader,androidx.savedstate,androidx.lifecycle.viewmodel,androidx.lifecycle.livedata,androidx.lifecycle.livedata.core,androidx.arch.core"/>
+
 	<supports-screens
         android:largeScreens="true"
         android:normalScreens="true"

android/build.gradle

@@ -10,6 +10,14 @@ androidGitVersion {
 	untrackedIsDirty = false
 }
 
+dependencies {
+	def appcompat_version = "1.2.0"
+
+	implementation "androidx.appcompat:appcompat:$appcompat_version"
+	// For loading and tinting drawables on older versions of the platform
+	implementation "androidx.appcompat:appcompat-resources:$appcompat_version"
+}
+
 android {
 	flavorDimensions "variant"
 

android/gradle.properties

@@ -1 +1,3 @@
 org.gradle.jvmargs=-Xmx1536M
+android.useAndroidX=true
+android.enableJetifier=true

gradle.properties

@@ -0,0 +1,3 @@
+org.gradle.jvmargs=-Xmx1536M
+android.useAndroidX=true
+android.enableJetifier=true

gradle/wrapper/gradle-wrapper.properties

@@ -4,3 +4,5 @@ distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
 distributionUrl=https\://services.gradle.org/distributions/gradle-6.5-all.zip
+android.useAndroidX=true
+android.enableJetifier=true