Restore missing IA32 7-Zip binary required by install script

[oalfroukh]

Summary

The install script (script/select-7z-arch.js) still attempts to select the IA32 7-Zip binary, but vendor/7z-ia32.exe and vendor/7z-ia32.dll are missing from the repository/package, causing installation to fail when targeting IA32.

This PR restores the missing binary required by the existing IA32 installation logic.

Fixes #612

However, these files ares no longer present in the repository/package, causing installation to fail with:

Error: ENOENT: no such file or directory, copyfile
'node_modules\electron-winstaller\vendor\7z-ia32.exe'
->
'node_modules\electron-winstaller\vendor\7z.exe'

Reproduction

• Node.js 22.22.3 (32-bit)
• Windows
• IA32 Electron build
• electron-builder 26.15.7 (through transitive dependency)

The installation fails during the electron-winstaller install script.

Adding back vendor/7z-ia32.exe and vendor/7z-ia32.dll fix the installation and allows the build to complete successfully.

This PR restores the missing binary required by the existing IA32 installation logic.

[dsanders11]

Hi @oalfroukh, thanks for the PR! We've clarified our support for building on 32-bit hosts in #614 (it's not supported), so I'm going to close this out.