cannot build on fresh systems

[plebhash]

while working on stratum-mining/sv2-apps#59 I noticed this CI failure

that made me realize that having bitcoin-capnp-types as a build dependency is introducing a new development pre-requisite, which I probably resolved a while ago on my workstation when first exploring capnproto development and never thought about it again, but now I'm being forced to re-visit this with more careful eyes

on a Ubuntu system, I can easily fix the CI error from the link above via apt-get install capnproto, but then the build errors become:

error: failed to run custom build command for `bitcoin-capnp-types v0.1.0 (https://github.com/2140-dev/bitcoin-capnp-types?rev=2ccda4c10554a204188d563eab707a8d07334b52#2ccda4c1)`

Caused by:
  process didn't exit successfully: `/home/ubuntu/sv2-apps/pool-apps/target/debug/build/bitcoin-capnp-types-9cbfcae8ba49f7a5/build-script-build` (exit status: 101)
  --- stdout
  cargo:rerun-if-changed=capnp

  --- stderr
  capnp/common.capnp:7:20-38: error: Import failed: /capnp/c++.capnp
  capnp/common.capnp:8:2-5: error: Not defined: Cxx
  capnp/proxy.capnp:7:20-38: error: Import failed: /capnp/c++.capnp
  capnp/proxy.capnp:8:2-5: error: Not defined: Cxx
  capnp/echo.capnp:7:20-38: error: Import failed: /capnp/c++.capnp
  capnp/echo.capnp:8:2-5: error: Not defined: Cxx
  capnp/init.capnp:7:20-38: error: Import failed: /capnp/c++.capnp
  capnp/init.capnp:8:2-5: error: Not defined: Cxx
  capnp/mining.capnp:7:20-38: error: Import failed: /capnp/c++.capnp
  capnp/mining.capnp:8:2-5: error: Not defined: Cxx

  thread 'main' (38362) panicked at /home/ubuntu/.cargo/git/checkouts/bitcoin-capnp-types-dd6f02671a2e5d84/2ccda4c/build.rs:11:10:
  called `Result::unwrap()` on an `Err` value: Error { kind: Failed, extra: "Error while trying to execute `capnp compile`: Premature end of file." }
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
warning: build failed, waiting for other jobs to finish...

which suggests some adaptations would be required to build.rs edit: turns out this can be solved on Ubuntu simply by installing libcapnp-dev in addition to capnproto, no need to touch build.rs... this is merely a documentation issue

ideally, we should think of something that works universally across most popular UNIX-based development platforms (e.g.: macOS and popular linux distros)

[plebhash]

turns out there's no need to touch build.rs, and this is just a suggestion for some kind of development pre-requisites section on README.md

[plebhash]

additionally, this is not really a blocker for stratum-mining/sv2-apps#59, as I initially reported

it's simply a nice-to-have suggestion of improvement that would help devs avoid little footguns while using this crate