* buildGoModule: don't inherit postBuild hook when building go-modules
This is a slight revert of 5ce647b8bf
(#212800).
Inheriting these hooks in the `.go-modules` derivation can be confusing:
One doesn't expect them to run when generating the fixed output modules
derivation, but only on the main derivation. A `postBuild` hook that
adds some files to $out will cause a very hard to debug issue[1].
This commit adds support for a dedicated `modPostBuild` hook that will
be used only by the derivation building `.go-modules`. Additionally,
`go.section.md` now explains these attributes behavior better.
[1]:
https://discourse.nixos.org/t/cant-update-a-go-package-getting-go-inconsistent-vendoring/27063/6
Co-authored-by: Sandro <sandro.jaeckel@gmail.com>
