--silent flag is not respected.

• Node Version: v14.15.1 and 7.5.4
• Platform: Darwin seko-mbp 20.6.0 Darwin Kernel Version 20.6.0: Wed Jun 23 00:26:31 PDT 2021; root:xnu-7195.141.2~5/RELEASE_X86_64 x86_64
• Compiler: Apple clang version 12.0.0 (clang-1200.0.32.21)
  Target: x86_64-apple-darwin20.6.0
  Thread model: posix
  InstalledDir: /Applications/Xcode_12.1.0.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin
• Module: general use via node api.

When used via node api, --silent flag is not respected. Code here https://github.com/nodejs/node-gyp/blob/master/lib/node-gyp.js#L170-L172

  if (!opts.silent && !opts.stdio) {
    opts.stdio = [0, 1, 2]
  }

is setting the stdio to inherit but this does not make it silent if the parent script is not silent.

in this situation, setting this to ['ignore', 'ignore', 'ignore'] might be better, which will make it truly silent. In it's current state output is reduced but it's still printing out unexpected lines in the terminal.

More information can be found here https://github.com/electron/electron-rebuild/issues/594

Start in lib/node-gyp.js at the stdio handling around lines 170-172, using the Node API path described in the issue. Reproduce a silent invocation and verify that the completed behavior suppresses the unexpected terminal output while preserving the stated non-silent behavior.