system-deps-v9.0.0

Fixed

• unset TARGET and PKG_CONFIG_ALLOW_CROSS after pkg-config has read them
• don't emit duplicate rustc-link-search lines
• add some information about what's happening with the new target arg to gen_flags

Other

• Reuse pkg_config v0.3.34's Library::extract_lib_from_filename
• Test static/target build with link_files
• Support pkg-config-rs link_files on static/target builds
• Remove release-drafter (superseded by release-plz)
• Fix broken changelog compare links for 8.0.0