Extract AppFuse as a util

Bug: 110379912
Test: testOpenProxyFileDescriptor
Change-Id: I0429a498d7b54682efe9b05815f3470e8745609e
diff --git a/Android.bp b/Android.bp
index 44e2317..b192b42 100644
--- a/Android.bp
+++ b/Android.bp
@@ -95,6 +95,7 @@
     ],
 
     srcs: [
+        "AppFuseUtil.cpp",
         "Benchmark.cpp",
         "CheckEncryption.cpp",
         "Checkpoint.cpp",