Log message:
Manipulate the buildlink depth so that libiconv and Xfixes aren't added
to BUILDLINK_DEPENDS unless their respective buildlink3.mk files are
included by the top-level Makefile.

Log message:
(re-add) buildlink2.mk needed for suggested fix for PR 24787.
(until qt3 is bl3ified)

Log message:
Split out the code that deals with checking whether the software is
built-in or not into a separate builtin.mk file.  The code to deal
checking for built-in software is much simpler to deal with in pkgsrc.

The buildlink3.mk file for a package will be of the usual format
regardless of the package, which makes it simpler for packagers to
update a package.

The builtin.mk file for a package must define a single yes/no variable
USE_BUILTIN.<pkg> that is used by bsd.buildlink3.mk to decide whether
to use the built-in software or to use the pkgsrc software.

Log message:
No longer used.

Log message:
Add BUILDLINK_DEPENDS.<pkg> for dependencies in a section that is invoked
only if we're not using the built-in versions of the package.

Log message:
Move the settings, which force the use of builtin versions of dependencies
if the builtin version of the package is being used, into a global
location so that they're always executed.

Log message:
If we're using the built-in version of the software, then we must also
be using built-in versions of any other software pulled in via
buildlink3.mk files.

Log message:
Reorder some lines so that BUILDLINK_USE_BUILTIN.<pkg> set in the
environment overrides all other settings.

Log message:
When using the native version of this library, symlink the .pc file into
the buildlink directory so that pkg-config can find it.  Ok'ed by jlam@.

Log message:
Don't include other buildlink3.mk files if we're just checking whether the
software is built-in.