arm: release worker centos7-arm64 uses GCC4.8

[refack]

Some new code was added in that exposed an stdlibc++4.8 bug that was fixed in 4.9
https://ci-release.nodejs.org/job/iojs+release/3855/nodes=centos7-arm64/
(Node minimal compiler has been gcc4.9 since node9)

/CC @nodejs/release @nodejs/build-infra

[refack]

As a result ATM we are not building nightlies for ARM7
e.g. https://ci-release.nodejs.org/job/iojs+release/3873/nodes=centos7-arm64/
And will probably fail for 11.x and maybe 10.x is one of several PR that require 4.9 get backported.
P.S. the test CI is setup all 4.9 so we will have now early indication.

/CC @jasnell @targos

P.P.S. I would fix it, but I don't have access to release machines.

[refack]

/CC @mhdawson @joaocgreis @rvagg @jbergstroem

P.S. it seems like the Ansible playbook is all set up, just need to run it on release-packetnet-centos7-arm64-1

[mhdawson]

I can run it, would just like @rvagg to confirm that he is comfortable that we just need to run the playbook.

[mhdawson]

In test I see that we have a number of different types of machines:

centos7-arm64-gcc48
centos7-arm64-gcc6

Not sure which versions of the compiler are used for
debian7-docker-armv7
debian8-docker-armv7
ubuntu1604-arm64

From the building docs minimum levels are:

GCC 4.9.4 for 8.X and higher
GCC 4.8.5 for 6.X

My key concern is that I think we may still need to build 6.x on 4.8.5 on the release machines and I don't see any compiler selection logic for ARM and we only have a single machine in the release CI for arm64

[refack]

centos7-arm64-gcc48
centos7-arm64-gcc6

AFAIK these are "virtual" tags that are used to select different version of devtoolset
gcc48 used the default devtoolset2
gcc6 does . /opt/rh/devtoolset-6/enabl

[mhdawson]

@gdams is looking at the ansible scripts to get on top of what compiler level is installed for centos7-arm64 based on the updated ansible scripts.

[mhdawson]

@refack good to know, but next question is if we have the equivalent for 4.9.4. I can see test-packetnet-centos7-arm64-1 has those 2 tags but don't see any 4.9.4 equivalent.

[gdams]

so we are running this to add gcc 4.9.4 on rhel7.x, Maybe we need the same logic on Centos7.x?

[mhdawson]

I think that might have been for IBM platforms since we did not believe there as a version of the redhat developer toolset available. It seems like there is a version on arm based on the tags and this in the ARM64 job in test

 if [[ "$nodes" =~ centos[67]-(arm)?64-gcc6 ]]; then
    exec_cmd=". /opt/rh/devtoolset-6/enable; $exec_cmd"
  fi

[gdams]

so the following are installed on centos7:

  centos7: [
    'ccache,gcc-c++,devtoolset-6,sudo',
  ],