Fix cross platform build

Dockerfile

@@ -1,21 +1,14 @@
 FROM debian
 
-ENV PATH=$PATH:/opt/Nim/bin:/root/.nimble/bin
+ENV PATH=$PATH:/root/.nimble/bin
 
 RUN apt update && \
-      apt -y install libc-dev gcc curl git perl mingw-w64 libzip-dev \
+      apt -y install libc-dev gcc curl git perl mingw-w64 libzip-dev wget \
       && \
       rm -rf /var/cache/apt/;
 
-RUN mkdir -p /opt && cd /opt && \
-      curl -LO https://github.com/nim-lang/Nim/archive/v0.18.0.tar.gz && \
-      tar zxf v0.18.0.tar.gz && rm -f v0.18.0.tar.gz && \
-      mv Nim-0.18.0 Nim && cd Nim && \
-      git clone --depth 1 git://github.com/nim-lang/csources && \
-      cd csources && sh build.sh && \
-      cd .. && ./bin/nim c koch && ./koch boot -d:release && \
-      nim e install_nimble.nims && \
-      rm -rf /opt/Nim/tests;
+RUN apt -y install xz-utils make
+RUN CHOOSENIM_CHOOSE_VERSION="0.18.0" curl https://nim-lang.org/choosenim/init.sh -sSf | bash -s -- "-y"
 
 ADD scripts /scripts
 ADD project /src