tests/docker: Install the NSIS tools in the MinGW capable images

tests/docker: Install the NSIS tools in the MinGW capable images

This fixes:

  $ make installer
  (cd /tmp/qemu-nsis; \
           for i in qemu-system-*.exe; do \
             arch=${i%.exe}; \
             arch=${arch#qemu-system-}; \
             echo Section \"$arch\" Section_$arch; \
             echo SetOutPath \"\$INSTDIR\"; \
             echo File \"\${BINDIR}\\$i\"; \
             echo SectionEnd; \
           done \
          ) >/tmp/qemu-nsis/system-emulations.nsh
  makensis -V2 -NOCD \
                  -DCONFIG_DOCUMENTATION="y" \
                   \
                  -DBINDIR="/tmp/qemu-nsis" \
                   \
                  -DSRCDIR="/home/phil/source/qemu" \
                  -DOUTFILE="qemu-setup-4.0.90.exe" \
                  -DDISPLAYVERSION="4.0.90" \
                  /home/phil/source/qemu/qemu.nsi
  /bin/sh: 1: makensis: not found
  Makefile:1077: recipe for target 'qemu-setup-4.0.90.exe' failed
  make: *** [qemu-setup-4.0.90.exe] Error 127

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20190715174817.18981-4-philmd@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>