[NFC][Docs] Update README.md with enhanced build instructions for CIRCT

[doofin]

Hi, this PR add more details about building specific part

[dobios]

While we're at it, we should probably also add the lld linker flag to the readme as it's rough to compiler llvm without it:

-DLLVM_ENABLE_LLD=ON

[dobios]

Don't want to make the wording more confusing in the readme, so here are a few suggestions.

[doofin]

Thanks @dobios , I applied your suggestions.

[dobios]

stray backslash

[dobios]

While we're at it, we should probably also add the lld linker flag to the readme as it's rough to compiler llvm without it:

-DLLVM_ENABLE_LLD=ON

I also suggest taking this comment into account

[doofin]

While we're at it, we should probably also add the lld linker flag to the readme as it's rough to compiler llvm without it:

-DLLVM_ENABLE_LLD=ON

I also suggest taking this comment into account

it's here https://github.com/llvm/circt/pull/9203/files?short_path=b335630#diff-b335630551682c19a781afebcf4d07bf978fb1f8ac04c6bf87428ed5106870f5

[TaoBi22]

While we're at it, we should probably also add the lld linker flag to the readme as it's rough to compiler llvm without it:

-DLLVM_ENABLE_LLD=ON

I also suggest taking this comment into account

Fly-by nit but lld isn't in our dependency list so I'm not sure we want it to depend in the default build command - might be worth documenting it as an option separately from the default command?

[dobios]

While we're at it, we should probably also add the lld linker flag to the readme as it's rough to compiler llvm without it:

-DLLVM_ENABLE_LLD=ON

I also suggest taking this comment into account

Fly-by nit but lld isn't in our dependency list so I'm not sure we want it to depend in the default build command - might be worth documenting it as an option separately from the default command?

@TaoBi22 isn't lld part of llvm?

[TaoBi22]

@TaoBi22 isn't lld part of llvm?

It is, but it's not built or installed by the existing command, so someone who doesn't have an existing lld install would still get hit by an opaque error following the instructions

[dobios]

@TaoBi22 isn't lld part of llvm?

It is, but it's not built or installed by the existing command, so someone who doesn't have an existing lld install would still get hit by an opaque error following the instructions

It's currently part of the "getting started" command though, and linking LLVM with the default linker requires something like 64Gb or memory, so it will crash for most systems without an absurd amount of swap. But yeah if you think it's best to leave it out, your reasoning does make sense

[doofin]

@dobios please help me merge this since it's approved, thanks!