Add: CONFIGURE_ARGS+=--with-harfbuzz=no

  Fixes the build on systems with a native harfbuzz library, where the
  library will otherwise be auto-detected.

Add: USE_TOOLS+=pkg-config

  Not identified as fixing any real-world problems, but it corrects build
  behaviour if buildlinking harfbuzz for diagnostic purposes.

Helps with working around the problems identified in PR pkg/48919.

No PKGREVISION bump - I believe all the problems fixed here prevent this
package from building at all if on an affected platform, and unaffected
platforms will not be affected by these changes.

(dsainty)