Document v8_symbol_level

Most places that mention blink_symbol_level as a possible optimization
should also mention v8_symbol_level. This change does that.

Bug: 1273644
Change-Id: Icdd64e684f61d6deeb983ac88e1eee5b7d6a59dd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3307360
Commit-Queue: Bruce Dawson <[email protected]>
Reviewed-by: Jesse McKenna <[email protected]>
Cr-Commit-Position: refs/heads/main@{#946115}
diff --git a/docs/linux/build_instructions.md b/docs/linux/build_instructions.md
index 5f8f75b..ef4c354 100644
--- a/docs/linux/build_instructions.md
+++ b/docs/linux/build_instructions.md
@@ -161,11 +161,12 @@
 line-by-line debugging. Setting `symbol_level=0` will include no debug
 symbols at all. Either will speed up the build compared to full symbols.
 
-#### Disable debug symbols for Blink
+#### Disable debug symbols for Blink and v8
 
 Due to its extensive use of templates, the Blink code produces about half
 of our debug symbols. If you don't ever need to debug Blink, you can set
-the GN arg `blink_symbol_level=0`.
+the GN arg `blink_symbol_level=0`. Similarly, if you don't need to debug v8 you
+can improve build speeds by setting the GN arg `v8_symbol_level=0`.
 
 #### Use Icecc