build: enable -fvisibility to improve startup speeds

[avivkeller]

cc @joyeecheung this resolves your TODO(joyeecheung): investigate if it breaks addons. comment.

If I understand correctly, this is fine to enable, since:

• All addon test suites pass against the build (on my mac)
• The removed strong symbols are declared only in internal headers under an internal namespace used only internslly. (With the addition of signo_string). Weak symbols don't matter here.

Plus, it speeds up startups by ~33% (yay!):

Running JS (--eval)

$ hyperfine --warmup 30 --runs 60 'node -e 0' './node -e 0'

Benchmark 1: node -e 0
  Time (mean ± σ):      61.6 ms ±  11.9 ms    [User:42.7 ms, System: 12.8 ms]
  Range (min … max):    45.9 ms … 108.5 ms    60 runs
 
Benchmark 2: ./node -e 0
  Time (mean ± σ):      45.4 ms ±   8.7 ms    [User:29.3 ms, System: 12.2 ms]
  Range (min … max):    31.2 ms …  79.3 ms    60 runs
 
Summary
  ./node -e 0 ran
    1.36 ± 0.37 times faster than node -e 0

--version Only

$ hyperfine --warmup 30 --runs 60 'node --version' './node --version'

Benchmark 1: node --version
  Time (mean ± σ):      36.9 ms ±  10.8 ms    [User:25.1 ms, System: 7.0 ms]
  Range (min … max):    25.7 ms …  83.5 ms    60 runs
 
Benchmark 2: ./node --version
  Time (mean ± σ):      23.6 ms ±  10.5 ms    [User:11.3 ms, System: 6.2 ms]
  Range (min … max):    11.0 ms …  65.4 ms    60 runs
 
Summary
  ./node --version ran
    1.56 ± 0.84 times faster than node --version

[nodejs-github-bot]

Review requested:

• @nodejs/gyp
• @nodejs/security-wg
• @nodejs/url
• @nodejs/v8-update

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.14%. Comparing base (18eaa73) to head (349d171).
⚠️ Report is 12 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #65526   +/-   ##
=======================================
  Coverage   90.13%   90.14%           
=======================================
  Files         751      751           
  Lines      253656   253679   +23     
  Branches    47787    47788    +1     
=======================================
+ Hits       228631   228668   +37     
- Misses      16258    16266    +8     
+ Partials     8767     8745   -22     

Files with missing lines	Coverage Δ
src/node.h	92.30% <ø> (ø)

... and 33 files with indirect coverage changes

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[joyeecheung]

All addon test suites pass against the build (on my mac)

The TODO is not about our addons, which aren't doing anything too sophisticated. We already know for example some Linux packages in the wild depend on Node.js for V8 symbols (may include internal ones). I suspect this may happen to e.g. libuv, OpenSSL etc. for embedders too. We also know that for example, some embedders rely on fast APIs even though we don't publish the header. The TODO is mostly about investigating this type of cases are out there. For simply removing the symbols, I'd prefer to see some more responsible investigation and coordination with downstream embedders/popular addons first before we pull the trigger.