docker: switch from kernel crosstools compilers to Debian cross-compilers

Now it is possible to build fully functional OpenBIOS binaries for all
architectures using the Debian cross-compiler packages, so switch the
builder image from the kernel crosstools compilers to the packaged
Debian cross-compilers.

Sigend-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
1 file changed