Add the ability to read config values from a multi-line file

[thoughtpolice]

While __SetConfig and __ListConfig are undocumented, they're very useful in my RV32 emulator. However, one thing I'd like to do is be able to set multiple configuration values at once in a file, e.g.

debug.disasm_ops=1
cpu.has_ext_m=1
cpu.has_ext_c=0
cpu.has_ext_a=0
cpu.has_ext_f=0

This could be inside the file rv32im-debug.conf, with the simulator being executed e.g.

./build/emu -e build/test.elf --config-file ./rv32im-debug.conf

The semantics would be as if the -C flag was used on the command line multiple times, and config options are applied sequentially (just the same as on the CLI).

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This would also dovetail nicely with the ability to read a config file from an environment variable; for example,

export SAIL_EMULATOR_CONFIG=$(pwd)/rv32im-debug.conf
./build/emu -e build/test.elf

But maybe that's not useful unless someone needs it.

[Alasdair]

Hi,

That's probably quite useful. I'll look into adding it.

The __SetConfig and __ListConfig functions so far only exist for command-line compatability with ARM's internal tools for when we run the AVS tests, but that's something we want to continue to be able to do so they won't be going away

[rmn30]

This overlaps with the functionality of riscv-config as used by the compliance group. I've implemented support for that in this PR: riscv/sail-riscv#43 but it requires recompiling the model to change the config so something like you propose might be simpler and preferable.