errno_restorer: Make bool operator explicit am: 64570d65f4 am: a11e28c0c2 am: 3bff6c9441 am: 5f00320641

Original change: https://android-review.googlesource.com/c/platform/system/libbase/+/1421480

Change-Id: If974c4301134f4961772c01bf71bbe15580d56a5
diff --git a/include/android-base/errno_restorer.h b/include/android-base/errno_restorer.h
index 1c8597c..2689505 100644
--- a/include/android-base/errno_restorer.h
+++ b/include/android-base/errno_restorer.h
@@ -30,7 +30,7 @@
   ~ErrnoRestorer() { errno = saved_errno_; }
 
   // Allow this object to be used as part of && operation.
-  operator bool() const { return true; }
+  explicit operator bool() const { return true; }
 
  private:
   const int saved_errno_;