Log Message:
pkgconf: update to 1.7.4.

Changes from 1.7.3 to 1.7.4:
---------------------------

* Bug fixes:
  - Fix null-dereference crash when pulling a malformed 'uninstalled'
    .pc file into a dependency tree.  Patch by Tobias Stöckmann.
  - Fix truncation of comment characters when quoted.
  - Fix handling of .pc module names in --list-all on Windows.
    Patch by Ryan Scott.
  - Handle platforms where realpath(3) requires a pre-allocated buffer.
    Patch by Fabian Groffen.
  - Fix version whitespace warning.
    Patch by Christoph Reiter.

* Enhancements:
  - Rewrite DOS paths on native Windows builds that don't use
    Cygwin/MSYS.
  - Add WantDefaultPure cross-compiler personality option.
  - Prefer --static --pure linking on Windows.
  - Add PKG_CONFIG_DONT_DEFINE_PREFIX environment variable.
    Patch by Jeff Moguillansky.
  - Many improvements when building pkgconf with Meson.
    Patches by Christoph Reiter.