Partially reland Auto-generate v8 version based on tags.

DEPS

Index: DEPS
diff --git a/DEPS b/DEPS
index edff128636dc5bcbeafc0fb9b97380e99883bccb..fc7d2d24e4aebc77573a52cd4e85723d91b96ff8 100644
--- a/DEPS
+++ b/DEPS
@@ -88,6 +88,11 @@ hooks = [
     'action': ['python', 'v8/tools/clang/scripts/update.py', '--if-needed'],
   },
   {
+    # Generate v8 version based on the last git tag.
+    "pattern": ".",
+    "action": ["python", "v8/build/generate_version.py"],
+  },
+  {
     # A change to a .gyp, .gypi, or to GYP itself should run the generator.
     "pattern": ".",
     "action": ["python", "v8/build/gyp_v8"],