build: fix c++ code coverage on macOS

[refack]

Alternative to #24004

Checklist

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

[nodejs-github-bot]

@refack sadly an error occured when I tried to trigger a build :(

[refack]

CI: https://ci.nodejs.org/job/node-test-pull-request/18809/
Coverage job (linux): https://ci.nodejs.org/job/node-test-commit-linux-coverage/841/

[refack]

/CC @nodejs/build-files @nodejs/gyp

[refack]

I tested this on https://ci.nodejs.org/computer/test-macstadium-macos10.12-x64-1/, and it builds and links
node.zip

But I get this from nyc:

> bash-3.2$ NODE_DEBUG=nyc ./node ./node_modules/.bin/nyc instrument --extension .js --extension .mjs --exit-on-error lib_/ lib/ > nyc.log 2> nyc.err
profiling: /Users/iojs/build/workspace/node/out/Release/obj.target/node_lib/src/async_wrap.gcda: cannot merge previous GCDA file: mismatched number of counters (10)
profiling: /Users/iojs/build/workspace/node/out/Release/obj.target/node_lib/src/async_wrap.gcda: cannot merge previous GCDA file: corrupt arc tag (0x344e496f)
.
.
.
Segmentation fault: 11

P.S. it's actually just the node binary:

> ./node -p 'process.version'
v12.0.0-pre
profiling: /Users/iojs/build/workspace/node/out/Release/obj.target/node_lib/src/async_wrap.gcda: cannot merge previous GCDA file: mismatched number of counters (10)
.
.
.

nyc.zip

[refack]

/CC @nodejs/build-files @nodejs/gyp (CI had just a flake)

[Trott]

Resume Build CI: https://ci.nodejs.org/job/node-test-pull-request/19111/

[Trott]

CI: https://ci.nodejs.org/job/node-test-pull-request/19115/ ✔️

[Trott]

Landed in eb6741b