openssl-sys crate failed other crate's build, with unhelpful error

I have a Windows 10 machine with Rust 1.69.0 installed, target list x86_64-pc-windows-msvc and wasm32-unknown-unknown. I wanted to install "wasm-pack". So I ran cargo install wasm-pack in CMD.EXE.

It did the cargo thing fo ra while, then terminated with:

   Compiling form_urlencoded v1.1.0
   Compiling unicode-normalization v0.1.22
error: failed to run custom build command for `openssl-sys v0.9.87`

Caused by:
  process didn't exit successfully: `C:\Users\Andi\AppData\Local\Temp\cargo-install9nib5Z\release\build\openssl-sys-2807ec8e19e2c176\build-script-main` (exit code: 101)
  --- stdout
  cargo:rerun-if-env-changed=X86_64_PC_WINDOWS_MSVC_OPENSSL_NO_VENDOR
  X86_64_PC_WINDOWS_MSVC_OPENSSL_NO_VENDOR unset
  cargo:rerun-if-env-changed=OPENSSL_NO_VENDOR
  OPENSSL_NO_VENDOR unset
  running "perl" "./Configure" "--prefix=C:\\Users\\Andi\\AppData\\Local\\Temp\\cargo-install9nib5Z\\release\\build\\openssl-sys-02242d1f2b328375\\out\\openssl-build\\install" "--openssldir=SYS$MANAGER:[OPENSSL]" "no-dso" "no-shared" "no-ssl3" "no-unit-test" "no-comp" "no-zlib" "no-zlib-dynamic" "no-md2" "no-rc5" "no-weak-ssl-ciphers" "no-camellia" "no-idea" "no-seed" "no-engine" "no-asm" "VC-WIN64A"

  --- stderr
  thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Error { kind: NotFound, message: "program not found" }', C:\Users\Andi\.cargo\registry\src\github.com-1ecc6299db9ec823\openssl-src-111.25.3+1.1.1t\src\lib.rs:504:39
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
warning: build failed, waiting for other jobs to finish...
error: failed to compile `wasm-pack v0.11.0`, intermediate artifacts can be found at `C:\Users\Andi\AppData\Local\Temp\cargo-install9nib5Z`

If I had to guess, I suspect this means I don't have OpenSSL dev libraries installed on my Windows machine. I see instructions in other issues in this github repo explaining how to point Cargo at OpenSSL. But that's not the problem. (It turns out I can just download binaries for wasm-pack anyway.) The problem is that this is a very, very bad error message. It doesn't explain to me what went wrong and it doesn't explain what I need to do or point me to a URL explaining what I need to do. It's just a raw panic. It seems like in other cases openssl-sys tries to catch failures such as this.

BTW I did a second build with RUST_BACKTRACE=1 and got

  --- stderr
  thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Error { kind: NotFound, message: "program not found" }', C:\Users\Andi\.cargo\registry\src\github.com-1ecc6299db9ec823\openssl-src-111.25.3+1.1.1t\src\lib.rs:504:39
  stack backtrace:
     0: std::panicking::begin_panic_handler
               at /rustc/84c898d65adf2f39a5a98507f1fe0ce10a2b8dbc/library\std\src\panicking.rs:579
     1: core::panicking::panic_fmt
               at /rustc/84c898d65adf2f39a5a98507f1fe0ce10a2b8dbc/library\core\src\panicking.rs:64
     2: core::result::unwrap_failed
               at /rustc/84c898d65adf2f39a5a98507f1fe0ce10a2b8dbc/library\core\src\result.rs:1750
     3: core::result::Result<T,E>::unwrap
     4: openssl_src::Build::build
     5: openssl_src::Build::build
     6: build_script_main::find_vendored::get_openssl
     7: build_script_main::env::{{closure}}
     8: build_script_main::find_openssl::{{closure}}
     9: core::ops::function::FnOnce::call_once
  note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

Reproduce the Windows build failure from the reported cargo install wasm-pack command, then inspect openssl-src/src/lib.rs around line 504 where the panic occurs. The change is complete when a missing program produces an actionable error instead of a raw unwrap panic.