Update build_command_buffer.py to copy libcommand_buffer_gles2.so from the correct dir on linux

Apparently the linux build now puts the library in chromium's output dir rather than a lib/ subdir.

TBR=borenet@google.com
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2165013003

Review-Url: https://codereview.chromium.org/2165013003
diff --git a/tools/build_command_buffer.py b/tools/build_command_buffer.py
index ee32587..015cdaf 100755
--- a/tools/build_command_buffer.py
+++ b/tools/build_command_buffer.py
@@ -137,8 +137,7 @@
     sys.exit('Error (ret code: %s) calling "%s" in %s' % (error.returncode,
         error.cmd, chrome_src_dir))
 
-  shared_lib_src_dir = os.path.join(chrome_src_dir, chrome_target_dir_rel,
-                                    shared_lib_subdir)
+  shared_lib_src_dir = os.path.join(chrome_src_dir, chrome_target_dir_rel)
   shared_lib_dst_dir = os.path.join(args.output_dir, shared_lib_subdir)
   # Make the subdir for the dst if does not exist
   if shared_lib_subdir and not os.path.isdir(shared_lib_dst_dir):