Remove unnecessary std::move

Moving a temporary object prevents copy elision, and could reduce
performance.

This fixes -Wpessimizing-move compiler warning.

Test: presubmit
Bug: 154270751
Change-Id: I4c769b174bb2a1fab2928c4887dcb70d82f264fa
diff --git a/libs/androidfw/PosixUtils.cpp b/libs/androidfw/PosixUtils.cpp
index 8ddc572..49ee8f7 100644
--- a/libs/androidfw/PosixUtils.cpp
+++ b/libs/androidfw/PosixUtils.cpp
@@ -119,7 +119,7 @@
       auto err = ReadFile(stderr[0]);
       result.stderr_str = err ? std::move(*err) : "";
       close(stderr[0]);
-      return std::move(result);
+      return result;
   }
 }