Merge changes from topic "gdb-prebuilts"

* changes:
  Remove obsolete parts of the build system.
  Switch to using a prebuilt GDB/gdbserver.
diff --git a/ndk/checkbuild.py b/ndk/checkbuild.py
index a0d942b..e8b53da 100755
--- a/ndk/checkbuild.py
+++ b/ndk/checkbuild.py
@@ -392,7 +392,8 @@
             shutil.rmtree(install_path)
         if not install_path.parent.exists():
             install_path.parent.mkdir(parents=True)
-        shutil.copytree(ClangToolchain.path_for_host(self.host), install_path)
+        shutil.copytree(ClangToolchain.path_for_host(self.host), install_path,
+                        symlinks=not self.host.is_windows)
 
         # clang-4053586 was patched in the prebuilts directory to add the
         # libc++ includes. These are almost certainly a different revision than