tests: Add Dockerfile containing dependencies for Emscripten build

The added Dockerfile is based on the emsdk image, which includes the
Emscripten toolchain. It also cross-compiles the necessary dependencies
(glib, libffi, pixman, and zlib) for the Emscripten target environment.

Signed-off-by: Kohei Tokunaga <ktokunaga.mail@gmail.com>
Link: https://lore.kernel.org/r/8bed6e9d46ef09328a87320928b5dec575d1e435.1745820062.git.ktokunaga.mail@gmail.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tests/docker/dockerfiles/emsdk-wasm32-cross.docker

@@ -0,0 +1,145 @@
+# syntax = docker/dockerfile:1.5
+
+ARG EMSDK_VERSION_QEMU=3.1.50
+ARG ZLIB_VERSION=1.3.1
+ARG GLIB_MINOR_VERSION=2.84
+ARG GLIB_VERSION=${GLIB_MINOR_VERSION}.0
+ARG PIXMAN_VERSION=0.44.2
+ARG FFI_VERSION=v3.4.7
+ARG MESON_VERSION=1.5.0
+
+FROM emscripten/emsdk:$EMSDK_VERSION_QEMU AS build-base
+ARG MESON_VERSION
+ENV TARGET=/builddeps/target
+ENV CPATH="$TARGET/include"
+ENV PKG_CONFIG_PATH="$TARGET/lib/pkgconfig"
+ENV EM_PKG_CONFIG_PATH="$PKG_CONFIG_PATH"
+ENV CFLAGS="-O3 -pthread -DWASM_BIGINT"
+ENV CXXFLAGS="$CFLAGS"
+ENV LDFLAGS="-sWASM_BIGINT -sASYNCIFY=1 -L$TARGET/lib"
+RUN apt-get update && apt-get install -y \
+    autoconf \
+    build-essential \
+    libglib2.0-dev \
+    libtool \
+    pkgconf \
+    ninja-build \
+    python3-pip
+RUN pip3 install meson==${MESON_VERSION} tomli
+RUN mkdir /build
+WORKDIR /build
+RUN mkdir -p $TARGET
+RUN <<EOF
+cat <<EOT > /cross.meson
+[host_machine]
+system = 'emscripten'
+cpu_family = 'wasm32'
+cpu = 'wasm32'
+endian = 'little'
+
+[binaries]
+c = 'emcc'
+cpp = 'em++'
+ar = 'emar'
+ranlib = 'emranlib'
+pkgconfig = ['pkg-config', '--static']
+EOT
+EOF
+
+FROM build-base AS zlib-dev
+ARG ZLIB_VERSION
+RUN mkdir -p /zlib
+RUN curl -Ls https://zlib.net/zlib-$ZLIB_VERSION.tar.xz | \
+    tar xJC /zlib --strip-components=1
+WORKDIR /zlib
+RUN emconfigure ./configure --prefix=$TARGET --static
+RUN emmake make install -j$(nproc)
+
+FROM build-base AS libffi-dev
+ARG FFI_VERSION
+RUN mkdir -p /libffi
+RUN git clone https://github.com/libffi/libffi /libffi
+WORKDIR /libffi
+RUN git checkout $FFI_VERSION
+RUN autoreconf -fiv
+RUN emconfigure ./configure --host=wasm32-unknown-linux \
+    --prefix=$TARGET --enable-static \
+    --disable-shared --disable-dependency-tracking \
+    --disable-builddir --disable-multi-os-directory \
+    --disable-raw-api --disable-docs
+RUN emmake make install SUBDIRS='include' -j$(nproc)
+
+FROM build-base AS pixman-dev
+ARG PIXMAN_VERSION
+RUN mkdir /pixman/
+RUN git clone  https://gitlab.freedesktop.org/pixman/pixman /pixman/
+WORKDIR /pixman
+RUN git checkout pixman-$PIXMAN_VERSION
+RUN <<EOF
+cat <<EOT >> /cross.meson
+[built-in options]
+c_args = [$(printf "'%s', " $CFLAGS | sed 's/, $//')]
+cpp_args = [$(printf "'%s', " $CFLAGS | sed 's/, $//')]
+objc_args = [$(printf "'%s', " $CFLAGS | sed 's/, $//')]
+c_link_args = [$(printf "'%s', " $LDFLAGS | sed 's/, $//')]
+cpp_link_args = [$(printf "'%s', " $LDFLAGS | sed 's/, $//')]
+EOT
+EOF
+RUN meson setup _build --prefix=$TARGET --cross-file=/cross.meson \
+    --default-library=static \
+    --buildtype=release -Dtests=disabled -Ddemos=disabled
+RUN meson install -C _build
+
+FROM build-base AS glib-dev
+ARG GLIB_VERSION
+ARG GLIB_MINOR_VERSION
+RUN mkdir -p /stub
+WORKDIR /stub
+RUN <<EOF
+cat <<'EOT' > res_query.c
+#include <netdb.h>
+int res_query(const char *name, int class,
+              int type, unsigned char *dest, int len)
+{
+    h_errno = HOST_NOT_FOUND;
+    return -1;
+}
+EOT
+EOF
+RUN emcc ${CFLAGS} -c res_query.c -fPIC -o libresolv.o
+RUN ar rcs libresolv.a libresolv.o
+RUN mkdir -p $TARGET/lib/
+RUN cp libresolv.a $TARGET/lib/
+
+RUN mkdir -p /glib
+RUN curl -Lks https://download.gnome.org/sources/glib/${GLIB_MINOR_VERSION}/glib-$GLIB_VERSION.tar.xz | \
+    tar xJC /glib --strip-components=1
+
+COPY --link --from=zlib-dev /builddeps/ /builddeps/
+COPY --link --from=libffi-dev /builddeps/ /builddeps/
+
+WORKDIR /glib
+RUN <<EOF
+CFLAGS="$CFLAGS -Wno-incompatible-function-pointer-types" ;
+cat <<EOT >> /cross.meson
+[built-in options]
+c_args = [$(printf "'%s', " $CFLAGS | sed 's/, $//')]
+cpp_args = [$(printf "'%s', " $CFLAGS | sed 's/, $//')]
+objc_args = [$(printf "'%s', " $CFLAGS | sed 's/, $//')]
+c_link_args = [$(printf "'%s', " $LDFLAGS | sed 's/, $//')]
+cpp_link_args = [$(printf "'%s', " $LDFLAGS | sed 's/, $//')]
+EOT
+EOF
+RUN meson setup _build --prefix=$TARGET --cross-file=/cross.meson \
+    --default-library=static --buildtype=release --force-fallback-for=pcre2 \
+    -Dselinux=disabled -Dxattr=false -Dlibmount=disabled -Dnls=disabled \
+    -Dtests=false -Dglib_debug=disabled -Dglib_assert=false -Dglib_checks=false
+# FIXME: emscripten doesn't provide some pthread functions in the final link,
+#        which isn't detected during meson setup.
+RUN sed -i -E "/#define HAVE_POSIX_SPAWN 1/d" ./_build/config.h
+RUN sed -i -E "/#define HAVE_PTHREAD_GETNAME_NP 1/d" ./_build/config.h
+RUN meson install -C _build
+
+FROM build-base
+COPY --link --from=glib-dev /builddeps/ /builddeps/
+COPY --link --from=pixman-dev /builddeps/ /builddeps/