Reduce closure size

[dtzSiFive]

Presently closure is 1.3G:

$ nix path-info -Sh circt
/nix/store/r2hwc36mxj5s0j35491v95fks8gq91ij-circt-1.12.0-git-dd2e912	  1.3G

Contributing factors, to look into:

• Use of static libraries (needs multiplexing 😉)
• Unneeded references to build-time deps (Assertions: error messages include full path)
• LLVM/MLIR are built as appropriate (mostly) for Nixpkgs, reduce the build config (host support, features)

Splitting inputs would also help (circt output path is 323M)

• Docs: 162M (50%)
• Libs: 55M (~17%)
• Some bins can be put into dev output. Largest is circt-lsp-server.

[dtzSiFive]

Some findings:

Building without assertions (LLVM, MLIR, CIRCT) reduces this 1.3G -> 725.4M (and drops refs to various outputs from MLIR/LLVM, only retaining the lib output for LLVM).

LLVM lib output is 408M, contributing significantly (408M).

Here's where the references are:

$ nix why-depends /nix/store/zkmk41g8pmzgc1j63yzgzx51jbhfzv38-circt-1.12.0-git-dd2e912 /nix/store/ysr5p0yd9jxl72w3kwi8yjik0d6j6jvn-llvm-git-ae87a3b-lib --all --precise
/nix/store/zkmk41g8pmzgc1j63yzgzx51jbhfzv38-circt-1.12.0-git-dd2e912
└───bin/circt-lsp-server: …12.0-git-dd2e912/lib:/nix/store/ysr5p0yd9jxl72w3kwi8yjik0d6j6jvn-llvm-git-ae87a3b-lib/lib:/nix/s…
    bin/circt-opt: …12.0-git-dd2e912/lib:/nix/store/ysr5p0yd9jxl72w3kwi8yjik0d6j6jvn-llvm-git-ae87a3b-lib/lib:/nix/s…
    bin/circt-reduce: …12.0-git-dd2e912/lib:/nix/store/ysr5p0yd9jxl72w3kwi8yjik0d6j6jvn-llvm-git-ae87a3b-lib/lib:/nix/s…
    bin/circt-translate: …12.0-git-dd2e912/lib:/nix/store/ysr5p0yd9jxl72w3kwi8yjik0d6j6jvn-llvm-git-ae87a3b-lib/lib:/nix/s…
    bin/esi-tester: …12.0-git-dd2e912/lib:/nix/store/ysr5p0yd9jxl72w3kwi8yjik0d6j6jvn-llvm-git-ae87a3b-lib/lib:/nix/s…
    bin/firtool: …12.0-git-dd2e912/lib:/nix/store/ysr5p0yd9jxl72w3kwi8yjik0d6j6jvn-llvm-git-ae87a3b-lib/lib:/nix/s…
    lib/libcirct-llhd-signals-runtime-wrappers.so.16git: …12.0-git-dd2e912/lib:/nix/store/ysr5p0yd9jxl72w3kwi8yjik0d6j6jvn-llvm-git-ae87a3b-lib/lib:/nix/s…
    → /nix/store/ysr5p0yd9jxl72w3kwi8yjik0d6j6jvn-llvm-git-ae87a3b-lib

These refs are due to use of libLLVM*.so, which is 137M of the -lib output's 408M.