Bump abc

[povik]

This pulls:

• &mfs fix: Address some &mfs crashes abc#30
• &if workaround: Fix Assertion using &if: `pCutSet->nCuts > 0' abc#31
• out-of-tree build support (ahead of switching abc to be a submodule)
• other upstream changes (including the one required for add support for using ABCs library merging when providing multiple liberty files #4340)

[povik]

That pesky WASM build -- good thing we added it to the CI. Next time I push for defining int system(const char *arg) { return -1; } instead of patching every occurrence of system() in ABC source.

[whitequark]

That pesky WASM build -- good thing we added it to the CI.

It's really easy to build it locally by the way--you can check out yowasp/yosys and run ./build.sh, it even downloads the toolchain for you. Just point the yosys-src submodule to whichever you like.