[goroyabu]

Summary

• install libf2c.pc metadata for the static runtime library
• keep relative GNUInstallDirs layouts relocatable through ${pcfiledir} while preserving explicit absolute destinations
• verify installed metadata structurally and exercise a relocated translate, compile, link, and run workflow when pkg-config is available

Related Issue

Closes #62

Verification

• cmake -S . -B build -DBUILD_TESTING=ON
• cmake --build build --parallel
• ctest --test-dir build --output-on-failure — 68/68 passed
• staged installation followed by tests/pkg_config/VerifyInstalledPkgConfig.cmake with REQUIRE_PKG_CONFIG=ON — passed after relocating the installation prefix
• generated metadata checked with lib64 and multi-level relative library directories
• git diff --check origin/main..HEAD

The Linux CI jobs require pkg-config. macOS jobs always perform structural metadata checks and perform the functional check when pkg-config or pkgconf is available.

Impact

Installs a new libf2c.pc public packaging interface. Consumers can compile and statically link f2c-generated C with pkg-config --cflags --static --libs libf2c. The module reports the repository package version and includes the Unix math library as a private static-link dependency.

Documentation

README documents discovery and use of the installed module. CONTRIBUTING documents the relocated staged-prefix verification expected for future metadata changes.

Checklist

• The change is focused on one coherent maintenance outcome.
• Relevant local verification has been run and reported above.
• User-facing workflows and supported behavior are documented when changed.
• No downloaded upstream archives, extracted vendor sources, build outputs, or generated files were committed unintentionally.