saner ordering of operations in the test-Dockerfile

test-in-docker/Dockerfile

@@ -6,16 +6,12 @@ WORKDIR /src
 
 RUN git clone https://git.savannah.nongnu.org/git/lwip.git
 
-RUN git clone https://github.com/toelke/lwip-ftpd.git
-
-COPY . lwip-ftpd
-
 ADD http://elm-chan.org/fsw/ff/arc/ff14.zip .
-
 RUN unzip -q ff14.zip -d ff
-
 RUN sed -i -e 's/FF_FS_RPATH[	 ]*0/FF_FS_RPATH 2/;s/FF_USE_MKFS[	 ]*0/FF_USE_MKFS 1/;' ff/source/ffconf.h
 
+COPY . lwip-ftpd
+
 WORKDIR /build
 
 RUN cmake /src/lwip-ftpd/test-in-docker/src && make -j