Update Docker flow

[disdi]

make sw-all fails for gcc version below gcc version 12.x . Prebuilt toolchain used in Dockerfile for workflow also fails.

Suggest to use prebuilt from here or build from source

[paulsc96]

Which version are you using exactly? Our doc specifies >= 11.2.0.

Sadly, the ISA strings accepted by RISC-V GCC are not stable across versions; there's nothing we can do about that.

[disdi]

I am able to build with gcc 12.x. Could you update Dockerfile which still uses gcc 8.3 so that it is consistent with your doc.