Infer nodedir for headerfiles from execPath

[johnpyp]

• Node Version: latest 18 / 20
• Platform: Linux arm64/x86_64
• Compiler: gcc
• Module: anything

(Didn't follow for the format as this is a general capability request, for any version)

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Following from #812 and reading through some of the code in lib/configure.js and https://github.com/nodejs/node-gyp/blob/main/lib/find-node-directory.js, could the general strategy of inferring the nodedir through a traversal from process.execPath work to automatically find headers files even when using non-standard installation locations of node?

In other words, infer the npm_config_nodedir from the execPath, instead of requiring users set it explicitly:

export npm_config_nodedir="/my/node/install/path/18.x.x/"

node-gyp ...

My main hesitation is I don't know if this could accidentally end up with false-positive identification in a lot of the cases for some reason, or otherwise break some ecosystem usage. It could also be behind a flag or variable like --infer-nodedir / npm_config_infer_nodedir if that's a concern, though of course preferably it could be a default.