Fix npm run sync when v8 is patched

[goodov]

Currently npm run sync has these issues:

1. unable to sync gclient-controlled repos when they have changes, for ex. when v8 is patched, it's impossible to complete npm run sync:

Syncing projects:  97% (136/140) src/third_party/webrtc                                                            
                                                                                                                   
src/v8 (ERROR)                                                                                                     
----------------------------------------                                                                           
[0:00:06] Started.                                                                                                 
[0:00:07] Finished running: git remote set-url --push origin https://chromium.googlesource.com/v8/v8.git           
running "git cat-file -e 3d67ad243ce92b9fb162cc85da1dc1a0ebe4c78b^^^^{commit}" in "E:\.gitcache\chromium.googlesour
e.com-v8-v8"                                                                                                       
[0:00:07] Finished running: git config remote.origin.url                                                           
[0:00:07] Finished running: git rev-list -n 1 HEAD                                                                 
[0:00:07] Finished running: git rev-parse --abbrev-ref=strict HEAD                                                 
----------------------------------------                                                                           
Error: 112>                                                                                                        
112> ____ src\v8 at 3d67ad243ce92b9fb162cc85da1dc1a0ebe4c78b                                                       
112>    You have unstaged changes.                                                                                 
112>    Please commit, stash, or reset.                                                                            
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2. gclient sync is always performed for src even when chromium update is not needed. We can avoid it by adding additional .gclient into brave dir to always sync brave-specific DEPS.
3. npm run sync doesn't support gclient sync -D