How to find out the source of non-linkage when build succeeds?

[Jerry1144]

Output of brew config

HOMEBREW_VERSION: 4.1.25-95-gb72421e
ORIGIN: https://mirrors.tuna.tsinghua.edu.cn/git/homebrew/brew.git
HEAD: b72421e25807b72eac4ed041d9ae3ced22f9c285
Last commit: 8 hours ago
Core tap origin: https://mirrors.tuna.tsinghua.edu.cn/git/homebrew/homebrew-core.git
Core tap HEAD: 919639859213910c67a723f513816d3e45959077
Core tap last commit: 3 hours ago
Core tap branch: master
Core tap JSON: 26 Feb 14:37 UTC
HOMEBREW_PREFIX: /usr/local
HOMEBREW_BOTTLE_DOMAIN: https://mirrors.tuna.tsinghua.edu.cn/homebrew-bottles
HOMEBREW_BREW_GIT_REMOTE: https://mirrors.tuna.tsinghua.edu.cn/git/homebrew/brew.git
HOMEBREW_CASK_OPTS: []
HOMEBREW_CORE_GIT_REMOTE: https://mirrors.tuna.tsinghua.edu.cn/git/homebrew/homebrew-core.git
HOMEBREW_MAKE_JOBS: 4
HOMEBREW_NO_AUTO_UPDATE: set
HOMEBREW_NO_INSTALL_FROM_API: set
HOMEBREW_SORBET_RUNTIME: set
Homebrew Ruby: 3.1.4 => /usr/local/Homebrew/Library/Homebrew/vendor/portable-ruby/3.1.4/bin/ruby
CPU: quad-core 64-bit sandybridge
Clang: 10.0.0 build 1000
Git: 2.17.2 => /Library/Developer/CommandLineTools/usr/bin/git
Curl: 7.54.0 => /usr/bin/curl
macOS: 10.13.6-x86_64
CLT: 10.1.0.0.1.1539992718
Xcode: N/A

Output of brew doctor

Warning: Some installed formulae are deprecated or disabled.
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Warning: You have unlinked kegs in your Cellar.
Leaving kegs unlinked can lead to build-trouble and cause formulae that depend on
those kegs to fail to run properly once built. Run `brew link` on these:
  cmake
  libavif
  webp

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Warning: You have uncommitted modifications to Homebrew/homebrew-core.
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should you later need to do so for some reason.
  cd /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core && git stash -u && git clean -d -f

Uncommitted files:
  MM Formula/lib/libavif.rb

Warning: Homebrew's "sbin" was not found in your PATH but you have installed
formulae that put executables in /usr/local/sbin.
Consider setting your PATH for example like so:
  echo 'export PATH="/usr/local/sbin:$PATH"' >> /Users/iamadmin/.bash_profile

Warning: Broken symlinks were found. Remove them with `brew cleanup`:
  /usr/local/opt/libavif

Description of issue

I'm trying to understand why my tests fail in the CI. Can anyone point me to the right direction?

The modified test do uses a new option --sharpyuv, enabled through linkage to libwebp at compile time (and is a runtime dependency). When that option is not enabled, passing such option triggers the same error message as seen in the CI outputs: conversion to YUV failed. (the next message is unrelated: conversion to YUV is part of file import, so when this step fails, file import fails)

Problem is, I've tried my best to help the build system find webp in the formula - the PKG_CONFIG_PATH line is totally not needed on my machine, and will cause build error if it came without corresponding depends_on "webp" and with an aom not depending on jpeg-xl; The depends_on "webp" isn't even needed in the first place - there's an indirect libavif-aom-jpeg-xl-webp chain of inclusion.

I have even explicitly passed-DAVIF_LIBSHARPYUV_ENABLED=1 in hope that it'd turn into a build-time failure if webp were not found. This does not work - if webp is not found the build proceeds as if it was not enabled, producing binary that fails the test. What else could I do to make the new dependency - and the updated test - work?