0.15.0 build failure with tectonic_bridge_harfbuzz on macOS (Apple Silicon)

[g4titanx]

i'm experiencing build failures when trying to compile a rust project that depends on tectonic 0.15.0 on macOS with Apple Silicon (M1/M2). The specific error occurs in the tectonic_bridge_harfbuzz dependency.

error: failed to run custom build command for `tectonic_bridge_harfbuzz v0.2.9`

Caused by:
  process didn't exit successfully: `/Users/g4titan/noteforge/backend/target/debug/build/tectonic_bridge_harfbuzz-93af2d9e1a93bceb/build-script-build` (exit status: 101)
  --- stderr
  thread 'main' panicked at /Users/g4titan/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tectonic_bridge_harfbuzz-0.2.9/build.rs:143:47:
  failed to copy header: Os { code: 2, kind: NotFound, message: "No such file or directory" }

i've tried:

• setting PKG_CONFIG_PATH to point to the Homebrew-installed dependencies
• installing all required dependencies via Homebrew
• creating symbolic links to the header files
• setting various environment variables (HARFBUZZ_INCLUDE_DIR, CPATH, etc.)

looking at the build script:
the error occurs at line 143 in the build.rs file for tectonic_bridge_harfbuzz:

// Around line 143
for entry in fs::read_dir(&src_dir).expect("failed to read dir") {
    let entry = entry.expect("failed to get dir entry");
    if entry.path().extension() == Some(OsStr::new("h")) {
        let hdest = dest_dir.join(entry.path().file_name().unwrap());
        fs::copy(entry.path(), hdest).expect("failed to copy header");
    }
}

it seems the build script is trying to copy header files from a source directory, but one or more of those files can't be found.

is there a known fix for this issue? are there specific environment variables I should set to help the build script find the required headers?

[doronbehar]

Already reported in #1263 .