Revert "libbinder: remove __ANDROID_APEX__ stability diff"

This reverts commit e9441bcf32c04901807748bde85f16444464eb91.

Reason for revert: b/180559880#comment7
Bug: 179906909

Change-Id: I04472d3bbe97c9c42df74c10ce87c176fa7098dd
diff --git a/libs/binder/Stability.cpp b/libs/binder/Stability.cpp
index b56e09f..339c538 100644
--- a/libs/binder/Stability.cpp
+++ b/libs/binder/Stability.cpp
@@ -76,12 +76,18 @@
 }
 
 Stability::Level Stability::getLocalLevel() {
-#ifdef __ANDROID_APEX__
-#error APEX can't use libbinder (must use libbinder_ndk)
-#endif
-
 #ifdef __ANDROID_VNDK__
-    return Level::VENDOR;
+    #ifdef __ANDROID_APEX__
+        // TODO(b/142684679) avoid use_vendor on system APEXes
+        #if !defined(__ANDROID_APEX_COM_ANDROID_MEDIA_SWCODEC__) \
+            && !defined(__ANDROID_APEX_TEST_COM_ANDROID_MEDIA_SWCODEC__)
+        #error VNDK + APEX only defined for com.android.media.swcodec
+        #endif
+        // TODO(b/142684679) avoid use_vendor on system APEXes
+        return Level::SYSTEM;
+    #else
+        return Level::VENDOR;
+    #endif
 #else
     // TODO(b/139325195): split up stability levels for system/APEX.
     return Level::SYSTEM;