Docker/C++ problem - Compiling Error /usr/bin/ld: cannot open output file server: Is a directory - c++

Question

I'm trying to compile a C++ program using cmake in ubuntu containerized in Docker. Without Docker I can make it work just fine, but with it I seem to get some errors, whowever I can't seem to fix them :/
I've tried resolving to change the path to many different combinations in the hopes that I was just writing in the wrong path.
FROM ubuntu:16.04
# Set the working directory to /app
WORKDIR /app
# Copy the current directory contents into the container at /app
COPY . /app
# Install any needed packages specified in the requirements.txt
RUN apt-get update && apt-get -y install g++ make cmake-curses-gui libsqlite3-dev libmariadb-client-lgpl-dev subversion
# Make port 8078 available to the world outside this container
EXPOSE 8078
# Retrieve EOServ and build it
RUN svn checkout svn://eoserv.net/eoserv/trunk/ /app/eoserv
RUN cd /app/eoserv && mkdir build && cd build
RUN cmake -G "Unix Makefiles" /app/eoserv
RUN make
# Run ./eoserv when the container launches
RUN /app/eoserv/eoserv
# Here I've tried several options like
# RUN ./eoserv
# RUN cd /app/eoserv && ./eoserv
Expected results would be an eoserv binary in desired folder, it works when I don't run it in the docker image, but cmake it all by itself, without Docker.
Actual results are:
[ 91%] Building C object CMakeFiles/eoserv.dir/tu/sha256.c.o
[100%] Linking CXX executable eoserv
/usr/bin/ld: cannot open output file eoserv: Is a directory
collect2: error: ld returned 1 exit status
CMakeFiles/eoserv.dir/build.make:305: recipe for target 'eoserv' failed
make[2]: *** [eoserv] Error 1
CMakeFiles/Makefile2:67: recipe for target 'CMakeFiles/eoserv.dir/all' failed
make[1]: *** [CMakeFiles/eoserv.dir/all] Error 2
Makefile:127: recipe for target 'all' failed
make: *** [all] Error 2
The command '/bin/sh -c make' returned a non-zero code: 2

Answer 1

The RUN instruction starts a new shell. So the commands you RUN previously will only be local to that shell, which includes things like cd, and the next RUN instruction will start a new shell without knowledge of the previous.
The instructions
RUN cd /app/eoserv && mkdir build && cd build
RUN cmake -G "Unix Makefiles" /app/eoserv
RUN make
needs to be combined into a single RUN instruction
RUN cd /app/eoserv && mkdir build && cd build && cmake -G "Unix Makefiles" /app/eoserv && make
You could of course write a script which runs the commands, and invoke that script with the RUN instruction.