docs: Document that 32-bit Windows is unsupported

Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: "Daniel P. Berrangé" <berrange@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-ID: <20240222130920.362517-2-peter.maydell@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>

docs/about/build-platforms.rst

@@ -139,6 +139,8 @@ unprivileged accounts can create symlinks if Developer Mode is enabled.
 When Developer Mode is not available/enabled, the SeCreateSymbolicLinkPrivilege
 privilege is required, or the process must be run as an administrator.
 
+Only 64-bit Windows is supported.
+
 .. _Homebrew: https://brew.sh/
 .. _MacPorts: https://www.macports.org/
 .. _MSYS2: https://www.msys2.org/

docs/about/removed-features.rst

@@ -659,6 +659,21 @@ This command didn't produce any output already. Removed with no replacement.
 The ``singlestep`` command has been replaced by the ``one-insn-per-tb``
 command, which has the same behaviour but a less misleading name.
 
+Host Architectures
+------------------
+
+System emulation on 32-bit Windows hosts (removed in 9.0)
+'''''''''''''''''''''''''''''''''''''''''''''''''''''''''
+
+Windows 11 has no support for 32-bit host installs, and Windows 10 did
+not support new 32-bit installs, only upgrades. 32-bit Windows support
+has now been dropped by the MSYS2 project. QEMU also is deprecating
+and dropping support for 32-bit x86 host deployments in
+general. 32-bit Windows is therefore no longer a supported host for
+QEMU.  Since all recent x86 hardware from the past >10 years is
+capable of the 64-bit x86 extensions, a corresponding 64-bit OS should
+be used instead.
+
 Guest Emulator ISAs
 -------------------