deps: disable V8 concurrent sparkplug compilation

It introduces process hangs on some platforms because Node.js doesn't
tear down V8 correctly.
Disable it while we work on a solution.

Refs: nodejs/node#47297
Refs: https://bugs.chromium.org/p/v8/issues/detail?id=13902
PR-URL: nodejs/node#47450
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: Michael Dawson <midawson@redhat.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com>

Author: targos

common.gypi

@@ -38,7 +38,7 @@
 
     # Reset this number to 0 on major V8 upgrades.
     # Increment by one for each non-official patch applied to deps/v8.
-    'v8_embedder_string': '-node.5',
+    'v8_embedder_string': '-node.6',
 
     ##### V8 defaults for Node.js #####
 

deps/v8/src/flags/flag-definitions.h

@@ -1118,7 +1118,7 @@ DEFINE_BOOL(baseline_batch_compilation, true, "batch compile Sparkplug code")
 DEFINE_BOOL_READONLY(concurrent_sparkplug, false,
                      "compile Sparkplug code in a background thread")
 #else
-DEFINE_BOOL(concurrent_sparkplug, ENABLE_SPARKPLUG_BY_DEFAULT,
+DEFINE_BOOL(concurrent_sparkplug, false,
             "compile Sparkplug code in a background thread")
 DEFINE_WEAK_IMPLICATION(future, concurrent_sparkplug)
 DEFINE_NEG_IMPLICATION(predictable, concurrent_sparkplug)