tests/docker: drop --link from COPYs in emsdk docker

As we need to build images in both docker and podman lets not have any
incompatibilities. I don't think it makes any major difference.

Reviewed-by: Kohei Tokunaga <ktokunaga.mail@gmail.com>
Message-ID: <20251117115523.3993105-2-alex.bennee@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>

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

@@ -115,8 +115,8 @@ 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/
+COPY --from=zlib-dev /builddeps/ /builddeps/
+COPY --from=libffi-dev /builddeps/ /builddeps/
 
 WORKDIR /glib
 RUN <<EOF
@@ -141,5 +141,5 @@ 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/
+COPY --from=glib-dev /builddeps/ /builddeps/
+COPY --from=pixman-dev /builddeps/ /builddeps/