build: remove .git folders when testing V8

[richardlau]

When running make test-v8 V8's gclient sync converts folders
under deps/v8/third_party into git repositories. Unfortunately
the files that were checked in under deps/v8/third_party/zlib
have been modified from the upstream Chromium repository (some
files have been deleted and there are whitespace differences in
some of the files that were kept) so whenever the Node.js source
tree is hard reset/checked out gclient sync notices there are
unstaged changes as the files in the Node.js source tree do not
match those of the upstream Chromium third party zlib commit.

Refs: nodejs/build#2256

cc @nodejs/v8-update @mmarchini

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• commit message follows commit guidelines

[richardlau]

So I'm not entirely comfortable with this fix but it's probably the quickest way to unbreak the V8 test jobs.

Since V8's build checks out third_party and there is a discrepancy between what we have checked in to our repository in deps/v8/third_party/zlib and the upstream commit

node/deps/v8/DEPS

Lines 264 to 265 in 4a6a5c3

	'v8/third_party/zlib':
	Var('chromium_url') + '/chromium/src/third_party/zlib.git'+ '@' + 'b9b9a5af7cca2e683e5f2aead8418e5bf9d5a7d5',

it means that the test job is not strictly testing the code we have checked in (because the files get replaced when the V8 build runs gclient sync).

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/30781/
V8 CI: https://ci.nodejs.org/job/node-test-commit-v8-linux/3030/

[richardlau]

The V8 CI is failing on LinuxONE while compiling V8 tests:
https://ci.nodejs.org/job/node-test-commit-v8-linux/3030/nodes=rhel7-s390x,v8test=v8test/console

15:12:38 ../../test/cctest/parsing/test-scanner-streams.cc: In function ‘void TestUtf8AdvanceUntilOverChunkBoundaries()’:
15:12:38 ../../test/cctest/parsing/test-scanner-streams.cc:334:12: error: ‘char* strncpy(char*, const char*, size_t)’ output truncated copying between 1 and 15 bytes from a string of length 15 [-Werror=stringop-truncation]
15:12:38      strncpy(buffer, unicode_utf8, i);
15:12:38      ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
15:12:38 ../../test/cctest/parsing/test-scanner-streams.cc: In function ‘void TestUtf8ChunkBoundaries()’:
15:12:38 ../../test/cctest/parsing/test-scanner-streams.cc:363:12: error: ‘char* strncpy(char*, const char*, size_t)’ output truncated copying between 1 and 15 bytes from a string of length 15 [-Werror=stringop-truncation]
15:12:38      strncpy(buffer, unicode_utf8, i);
15:12:38      ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
15:12:38 cc1plus: all warnings being treated as errors

I believe the stringop-truncation warning is new to g++ 8 (we recently updated the Centos7/RHEL7 CI hosts to use devtoolset-8 for Node.js 14+) but then we're not seeing it on ppcle (https://ci.nodejs.org/job/node-test-commit-v8-linux/3030/nodes=centos7-ppcle,v8test=v8test/) and both are using g++ (GCC) 8.3.1 20190311 (Red Hat 8.3.1-3).

In any case I don't think it's been caused by this PR and was rather masked due to the V8 job being broken since we landed the V8 8.1 update. I'll defer to @nodejs/v8-update as to whether this failure blocks this PR from landing.

(We don't see this compile failure in the regular CI as we don't build V8 tests there.)

cc FYI @nodejs/platform-s390

[mmarchini]

Build worked for a while after landing 8.1, so it probably broke due to some upstream changes afterwards. But I agree, this was likely masked by the build failures. We can work to fix it after this PR lands.

[mmarchini]

Can we fast-track this to unbreak the CI?

[mmarchini]

Landed in 6d77df8