Always setup the native bridge library

... even if the string is empty. This will initialize the native bridge
library but mark it as unavailable.

- also, rename native_bridge_library_path to
native_bridge_library_filename to be closer to the actual meaning (it's
just the filename without any path).

Bug: 16404669

(cherry picked from commit I94628639691459d48d1fbf0841f36b68d51818e7)

Change-Id: I94628639691459d48d1fbf0841f36b68d51818e7
diff --git a/runtime/runtime.h b/runtime/runtime.h
index 34ccdcb..259691a 100644
--- a/runtime/runtime.h
+++ b/runtime/runtime.h
@@ -617,13 +617,14 @@
   bool implicit_so_checks_;         // StackOverflow checks are implicit.
   bool implicit_suspend_checks_;    // Thread suspension checks are implicit.
 
-  // The path to the native bridge library. If this is not empty the native bridge will be
-  // initialized and loaded from the pointed path.
+  // The filename to the native bridge library. If this is not empty the native bridge will be
+  // initialized and loaded from the given file (initialized and available). An empty value means
+  // that there's no native bridge (initialized but not available).
   //
   // The native bridge allows running native code compiled for a foreign ISA. The way it works is,
   // if standard dlopen fails to load native library associated with native activity, it calls to
   // the native bridge to load it and then gets the trampoline for the entry to native activity.
-  std::string native_bridge_library_path_;
+  std::string native_bridge_library_filename_;
 
   // Native bridge library runtime callbacks. They represent the runtime interface to native bridge.
   //