Enables symetric-multi-processor support in the Linux kernel configuration
used as base for the driver ports for PC. This is done to be compliant with
common usage of x86 drivers today.
Moreover, this commit uses the original kernel source for softirq/tasklet
implementation to get rid of the insufficient shadow implementation
in the lx_emul sources.
Ref genodelabs/genode#4562
This commit contains:
* Minimal Linux kernel target: pc_linux
* Library to generate a Linux build directory, config, generated headers
* API depot package
The actual work was provided by Josef Soentgen.
Ref genodelabs/genode#4416