tests/docker: update test-mingw to run single build

While the test-build test happily run for mingw the test-mingw case
runs more of the packaging inline with what our CI does. It however
fails if we don't find both compilers and expects to be run on a
docker image with both.

Remove that distinction and make it work more like the other build
test scripts.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20221027183637.2772968-3-alex.bennee@linaro.org>

tests/docker/test-mingw

@@ -13,14 +13,12 @@
 
 . common.rc
 
-requires_binary x86_64-w64-mingw32-gcc
-requires_binary i686-w64-mingw32-gcc
+requires_binary x86_64-w64-mingw32-gcc i686-w64-mingw32-gcc
 
 cd "$BUILD_DIR"
 
-for prefix in x86_64-w64-mingw32- i686-w64-mingw32-; do
-    TARGET_LIST=${TARGET_LIST:-$DEF_TARGET_LIST} \
-        build_qemu --cross-prefix=$prefix \
+TARGET_LIST=${TARGET_LIST:-$DEF_TARGET_LIST} \
+build_qemu \
         --enable-trace-backends=simple \
         --enable-gnutls \
         --enable-nettle \
@@ -29,8 +27,6 @@ for prefix in x86_64-w64-mingw32- i686-w64-mingw32-; do
         --enable-bzip2 \
         --enable-guest-agent \
         --enable-docs
-    install_qemu
-    make installer
-    make clean
-
-done
+install_qemu
+make installer
+make clean