Windows x86 (32-bit) is a metafamily of graphical operating systems developed and marketed by Microsoft. Using host OS (Windows, Linux 32/64 or Mac OS X) you can build native application for Windows x86 platform.
For more detailed information please visit vendor site.
Examples are listed from Windows x86 development platform repository:
; Latest stable version, NOT recommended ; Pin the version as shown below [env:latest_stable] platform = windows_x86 ; Specific version [env:custom_stable] platform = email@example.com
[env:upstream_develop] platform = https://github.com/platformio/platform-windows_x86.git
MinGW - Minimalist GNU for Windows