Replace build-essential with gcc, make, libc6-dev

We don't need a C++ compiler and Debian package development tools by now

Dockerfile

 FROM ubuntu:19.04
 
-RUN ln -fs /usr/share/zoneinfo/Europe/Berlin /etc/localtime && apt-get update -qq && apt-get install -y -qq build-essential git bison flex tcl cmake gcc-arm-linux-gnueabihf gcc-mingw-w64-x86-64 binutils-mingw-w64-x86-64
+RUN ln -fs /usr/share/zoneinfo/Europe/Berlin /etc/localtime && apt-get update -qq && apt-get install -y -qq gcc libc6-dev make git bison flex tcl cmake gcc-arm-linux-gnueabihf gcc-mingw-w64-x86-64 binutils-mingw-w64-x86-64