A simple Dockerfile and build script for building the xtensa-lx106-elf toolchain required by esp-open-rtos. Note that this toolchain is experimental, featuring very recent GCC (7.2.0). Newlib 2.0.0 is built, but this is mainly to enable building the C++ compiler. esp-open-rtos includes its own newlib.
Uses crosstool-NG for toolchain generation, accompanied with the xtensa-lx106 overlay and patches (under directory overlays and local-patches) acquired from Max Filippov's repository.
The container also has lx106-hal built from tommie's repo, available to the compiler.