ART: Remove unique_ptr release warnings

Do not release and create, just use assignment or constructor.

Bug: 32619234
Test: m test-art-host
Change-Id: I8b2bb87a0b6587ead41458ef00e27b7e61eeaff7
diff --git a/runtime/dex_file.cc b/runtime/dex_file.cc
index 3d68af1..aace8eb 100644
--- a/runtime/dex_file.cc
+++ b/runtime/dex_file.cc
@@ -204,7 +204,7 @@
                                                  verify_checksum,
                                                  error_msg);
   if (dex_file != nullptr) {
-    dex_file->mem_map_.reset(map.release());
+    dex_file->mem_map_ = std::move(map);
   }
   return dex_file;
 }
@@ -323,7 +323,7 @@
                                                  verify_checksum,
                                                  error_msg);
   if (dex_file != nullptr) {
-    dex_file->mem_map_.reset(map.release());
+    dex_file->mem_map_ = std::move(map);
   }
 
   return dex_file;
@@ -397,7 +397,7 @@
     }
     return nullptr;
   }
-  dex_file->mem_map_.reset(map.release());
+  dex_file->mem_map_ = std::move(map);
   if (!dex_file->DisableWrite()) {
     *error_msg = StringPrintf("Failed to make dex file '%s' read only", location.c_str());
     *error_code = ZipOpenErrorCode::kMakeReadOnlyError;