Android: Use JNI for getting post-processsing shaders

The Java implementation of getting the list of post-processing
shaders only looked in the Sys folder and not the User folder.
This could be fixed in the Java implementation, but it's
simpler to just call the C++ implementation instead.

Source/Android/jni/Config/PostProcessing.cpp

@@ -0,0 +1,35 @@
+// Copyright 2021 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#include <string>
+#include <vector>
+
+#include <jni.h>
+
+#include "VideoCommon/PostProcessing.cpp"
+#include "jni/AndroidCommon/AndroidCommon.h"
+
+extern "C" {
+
+JNIEXPORT jobjectArray JNICALL
+Java_org_dolphinemu_dolphinemu_features_settings_model_PostProcessing_getShaderList(JNIEnv* env,
+                                                                                    jclass)
+{
+  return VectorToJStringArray(env, VideoCommon::PostProcessing::GetShaderList());
+}
+
+JNIEXPORT jobjectArray JNICALL
+Java_org_dolphinemu_dolphinemu_features_settings_model_PostProcessing_getAnaglyphShaderList(
+    JNIEnv* env, jclass)
+{
+  return VectorToJStringArray(env, VideoCommon::PostProcessing::GetAnaglyphShaderList());
+}
+
+JNIEXPORT jobjectArray JNICALL
+Java_org_dolphinemu_dolphinemu_features_settings_model_PostProcessing_getPassiveShaderList(
+    JNIEnv* env, jclass)
+{
+  return VectorToJStringArray(env, VideoCommon::PostProcessing::GetPassiveShaderList());
+}
+}