Docker images for CI

Filesystem layout

Docker Toolbox on Windows

Cross toolchains

Generating a `.defconfig` file

Toolchain configuration

`arm-linux-gnueabi.defconfig`

`arm-linux-gnueabihf.defconfig`

`armv7-linux-gnueabihf.defconfig`

`aarch64-linux-gnu.defconfig`

`i586-linux-gnu.defconfig`

`loongarch64-linux-gnu.defconfig`

`mips-linux-gnu.defconfig`

`mipsel-linux-gnu.defconfig`

`mips64-linux-gnu.defconfig`

`mips64el-linux-gnu.defconfig`

`powerpc-linux-gnu.defconfig`

`powerpc64-linux-gnu.defconfig`

`riscv64-unknown-linux-gnu.defconfig`

`s390x-linux-gnu.defconfig`