[PATCH 12/12] docs: add information on how to setup build environments

[Pierrick Bouvier <pierrick.bouvier@linaro.org>]

MacOS and Linux are straightforward, but Windows needs a bit more
details.

Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
---
 docs/about/build-platforms.rst |   4 +-
 docs/devel/build-system.rst    | 100 +++++++++++++++++++++++++++++++++
 2 files changed, 103 insertions(+), 1 deletion(-)

diff --git a/docs/about/build-platforms.rst b/docs/about/build-platforms.rst
index 8fd7da140a3..fd1a8cabe36 100644
--- a/docs/about/build-platforms.rst
+++ b/docs/about/build-platforms.rst
@@ -29,6 +29,9 @@ The `Repology`_ site is a useful resource to identify
 currently shipped versions of software in various operating systems,
 though it does not cover all distros listed below.
 
+You can find how to install build dependencies for different systems on the
+:ref:`setup-build-env` page.
+
 Supported host architectures
 ----------------------------
 
@@ -118,7 +121,6 @@ Optional build dependencies
   cross compilation using ``docker`` or ``podman``, or to use pre-built
   binaries distributed with QEMU.
 
-
 Windows
 -------
 
diff --git a/docs/devel/build-system.rst b/docs/devel/build-system.rst
index d42045a2325..fa5601fed82 100644
--- a/docs/devel/build-system.rst
+++ b/docs/devel/build-system.rst
@@ -595,3 +595,103 @@ Built by Makefile:
   meson.build.  The rules are produced from Meson's JSON description of
   tests (obtained with "meson introspect --tests") through the script
   scripts/mtest2make.py.
+
+.. _setup-build-env:
+
+Setup build environment
+=======================
+
+Linux
+-----
+
+Fedora
+++++++
+
+::
+
+    sudo dnf update && sudo dnf builddep qemu
+
+Debian/Ubuntu
++++++++++++++
+
+You first need to enable `Sources List <https://wiki.debian.org/SourcesList>`_.
+Then, use apt to install dependencies:
+
+::
+
+    sudo apt update && sudo apt build-dep qemu
+
+MacOS
+-----
+
+You first need to install `Homebrew <https://brew.sh/>`_. Then, use it to
+install dependencies:
+
+::
+
+    brew update && brew install $(brew deps --include-build qemu)
+
+Windows
+-------
+
+You first need to install `MSYS2 <https://www.msys2.org/>`_.
+MSYS2 offers `different environments <https://www.msys2.org/docs/environments/>`_.
+x86_64 environments are based on GCC, while aarch64 is based on Clang.
+
+We recommend to use UCRT64 for windows-x86_64 and CLANGARM64 for windows-aarch64
+(only available on windows-aarch64 hosts).
+
+Then, you can open a windows shell, and enter msys2 env using:
+
+::
+
+    c:/msys64/msys2_shell.cmd -defterm -here -no-start -ucrt64
+    # Replace -ucrt64 by -clangarm64 or -mingw64 for other environments.
+
+MSYS2 package manager does not offer a built-in way to install build
+dependencies. You can start with this list of packages using pacman:
+
+Note: Dependencies need to be installed again if you use a different MSYS2
+environment.
+
+::
+
+    # update MSYS2 itself, you need to reopen your shell at the end.
+    pacman -Syu
+    pacman -S \
+        base-devel binutils bison diffutils flex git grep make sed \
+        ${MINGW_PACKAGE_PREFIX}-toolchain \
+        ${MINGW_PACKAGE_PREFIX}-glib2 \
+        ${MINGW_PACKAGE_PREFIX}-gtk3 \
+        ${MINGW_PACKAGE_PREFIX}-libnfs \
+        ${MINGW_PACKAGE_PREFIX}-libssh \
+        ${MINGW_PACKAGE_PREFIX}-ninja \
+        ${MINGW_PACKAGE_PREFIX}-pixman \
+        ${MINGW_PACKAGE_PREFIX}-pkgconf \
+        ${MINGW_PACKAGE_PREFIX}-python \
+        ${MINGW_PACKAGE_PREFIX}-SDL2 \
+        ${MINGW_PACKAGE_PREFIX}-zstd
+
+If you want to install all dependencies, it's possible to use recipe used to
+build QEMU in MSYS2 itself.
+
+::
+
+    pacman -S wget
+    wget https://raw.githubusercontent.com/msys2/MINGW-packages/refs/heads/master/mingw-w64-qemu/PKGBUILD
+    # Some packages may be missing for your environment, installation will still
+    # be done though.
+    makepkg -s PKGBUILD || true
+
+Build on windows-aarch64
+++++++++++++++++++++++++
+
+When trying to cross compile meson for x86_64 using UCRT64 or MINGW64 env,
+configure will run into an error because the cpu detected is not correct.
+
+Meson detects x86_64 processes emulated, so you need to manually set the cpu,
+and force a cross compilation (with empty prefix).
+
+::
+
+    ./configure --cpu=x86_64 --cross-prefix=
-- 
2.39.5