+1 on bumping to NodeJS v8.
The root cause is indeed an ill-formed NodeJS source code. Using older gcc to build it isn't a proper solution.
According to [2] the NodeJS v6 "active LTS" period ends at April 2018, however this is a build-related bug, and the GitHub issue is closed with resolution "fixed in next v7 release" (note that v7 is not LTS).
Even though NodeJS v8 "active LTS" period starts at October 2017 (in ~4 months), I'm OK with us bumping to v8 now.
(If we face any problems with v8, we can "downgrade" to v7 if necessary.)
Regards,
Vojtech