libproc.h file not found fix: ducktape include directories so that builds on mac os are successful

[jrabinow]

Compiling libproc v0.12.0
error: failed to run custom build command for `libproc v0.12.0`

Caused by:
  process didn't exit successfully: `<PROJECT PATH>/target/debug/build/libproc-7ab682cfcd895988/build-script-build` (exit status: 101)
  --- stderr
  <HOME>/.cargo/registry/src/github.com-1ecc6299db9ec823/libproc-0.12.0/libproc_rs.h:1:10: fatal error: 'libproc.h' file not found
  <HOME>/.cargo/registry/src/github.com-1ecc6299db9ec823/libproc-0.12.0/libproc_rs.h:1:10: fatal error: 'libproc.h' file not found, err: true
  thread 'main' panicked at 'Failed to build libproc bindings: ()', <HOME>/.cargo/registry/src/github.com-1ecc6299db9ec823/libproc-0.12.0/build.rs:9:10
  stack backtrace:
     0: rust_begin_unwind
               at /rustc/62b272d25c5bb8b6bb8ac73797d82b8b9a1eabda/library/std/src/panicking.rs:584:5
     1: core::panicking::panic_fmt
               at /rustc/62b272d25c5bb8b6bb8ac73797d82b8b9a1eabda/library/core/src/panicking.rs:142:14
     2: core::result::unwrap_failed
               at /rustc/62b272d25c5bb8b6bb8ac73797d82b8b9a1eabda/library/core/src/result.rs:1805:5
     3: core::result::Result<T,E>::expect
               at /rustc/62b272d25c5bb8b6bb8ac73797d82b8b9a1eabda/library/core/src/result.rs:1055:23
     4: build_script_build::main
               at ./build.rs:6:20
     5: core::ops::function::FnOnce::call_once
               at /rustc/62b272d25c5bb8b6bb8ac73797d82b8b9a1eabda/library/core/src/ops/function.rs:248:5
  note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

Also see #82

Test plan:

• $ make: build is successful
• test suite passes

[andrewdavidmackenzie]

Thanks @jrabinow for the contribution. I will publish a new patch version on crates.io after this.
Subscribe to releases in GH notifications if you want.

FYI @micouy @sporkmonger