update to 8.4.371.19

This requires changing our checkout strategy to check out the branch-heads branch (as documented at https://v8.dev/docs/version-numbers) instead of using the 8.4.371 branch, which never gets patches (it's always locked to 8.4.371.0).

We could also specify the v8 patch version manually, and i'm open to doing that, just wanted to do this to get it working.

ext/libv8/builder.rb

@@ -65,7 +65,7 @@ module Libv8
     # then this will be 4.5.95
     #
     def source_version
-      Libv8::VERSION.gsub(/\.[^.]+$/, '')
+      Libv8::V8_MINOR_VERSION
     end
 
     ##
@@ -84,7 +84,7 @@ module Libv8
 
         Dir.chdir('v8') do
           system 'git fetch origin'
-          unless system "git checkout #{source_version}"
+          unless system "git checkout branch-heads/#{source_version}"
             fail "unable to checkout source for v8 #{source_version}"
           end
           system "gclient sync" or fail "could not sync v8 build dependencies"

lib/libv8/version.rb

@@ -1,3 +1,4 @@
 module Libv8
-  VERSION = "7.3.495.0"
+  V8_MINOR_VERSION = "8.4"
+  VERSION = "8.4.371.0"
 end

vendor/depot_tools

@@ -1 +1 @@
-Subproject commit 9c0620120980e4c247ff8325ee8bbdcd4d9576e0
+Subproject commit 3229d944bfb4bc5983785f49cbc58f78872d8cb8