Short summary and FAQ regarding "buildlink2".
This file is meant to be included by bsd.pkg.mk and its main purpose is to
implement the targets used to generate the buildlink2 wrapper scripts and
to fix up libtool files after they are created.  The functionality is
triggered by defining USE_BUILDLINK2_ONLY in a package Makefile.
Make this file buildlink2-aware:

1) Include bsd.post-buildlink2.mk.

2) Instead of symlinking ${LIBTOOL} in the LTCONFIG/LIBTOOL_OVERRIDE
   sections, symlink ${PKGLIBTOOL} which defaults to ${LIBTOOL} but is
   set to the libtool wrapper script by bsd.post-buildlink2.mk.

3) Invent "BUILDLINK_X11PKG_DIR", which is only used (so far) to aid in
   fixing libtool archives by identifying package paths that are actually
   in ${X11BASE}.
This Makefile fragment is included by package buildlink2.mk files.  This
file defines a macro target, _BUILDLINK_USE, that symlinks package files
into a new hierarchy under ${BUILDLINK_DIR};
Minor punctuation nit.
New buildlink2.mk files for pthread and motif handling.
Use the buildlink2.mk file instead if USE_BUILDLINK2_ONLY is defined.
Explicitly remove "-I/usr/include" and "-L/usr/lib" as they're redundant.
Protect x11-links against recursively depending on itself.
XXX Perhaps this should be solved the same way as xpkgwedge?
Move the inclusion of bsd.post-buildlink2.mk earlier so that any
BUILD_DEPENDencies will be found by the other code in bsd.pkg.mk.
Minimize the amount of stuff protected by USE_LIBTOOL so that packages
like devel/zlib can more easily duplicate the effects of USE_LIBTOOL
without having to define it.
Invent new variable "CONFIGURE_DIRS" that is a list of directories in
which to execute the configure script in the do-configure target.  It
defaults to ${WRKSRC}.

XXX This needs to be generalized a bit to allow for different arguments
XXX to be passed to the configure script...not sure how, though.
First pass at conversion of various packages to use the buildlink2
framework.  Add many buildlink2.mk files to add to the framework.  Please
see buildlink2.txt for more details.
Add buildlink2.mk files to grow the buildlink2 framework.
* Reimplement the wrapper script system so that it examines each argument
  and translates it into its buildlink equivalent, with caching to reduce
  the penalty of the translation.  This makes the wrappers robust against
  having quotes or spaces in the arguments, e.g. -DCPP=\"cc\ -E\".  A more
  complete description of the wrapper script system may be found in
  mk/buildlink2/README.

* Push the libtool fixes into a separate main wrapper script so that the
  archives are fixed as part of the creation of the libtool archive, and so
  from make(1)'s point of view, the libtool archive is created atomically.
  This prevents accidentally triggerring rebuilds of uninstalled libtool
  archives that depend on other uninstalled libtool archives during the
  installation process.

* Use a new variable name convention in the buildlink framework:

	_LT_* are private libtool-related variables
	LIBTOOL are publicly-usable libtool-related variables
	_BLNK_* are private buildlink-related variables
	BUILDLINK_* are publicly-usable buildlink-related variables
Update to reflect changes from using the caching wrapper scripts.
* Convert some more packages to use the buildlink2 framework.
* Re-add EVAL_PREFIX lines that I shouldn't have removed from the
  buildlink2.mk files.
* Add several more new buildlink2.mk files to facilitate converting more
  packages.
Add a separate "buildlink" target on which to attach all of the buildlink
work.  Conceptually, it occurs after "patch" and before "configure".  Also
include bsd.buildlink2.mk instead of bsd.post-buildlink2.mk as the two will
merge into one file and move to another location.
Merge bsd.buildlink2.mk and bsd.post-buildlink2.mk into one file and store
in a new location (buildlink2/bsd.buildlink2.mk).  This file is directly
included by bsd.pkg.mk and _should_not_ be included by individual
buildlink2.mk files anymore.

A new variable has been created to handle different types of dependencies
on packages:

BUILDLINK_DEPMETHOD.<pkg> is either "build" or "full" (default is "full")
and represents whether we desire a BUILD_DEPENDS or a DEPENDS on <pkg>.

Also, the libtool.sh script has been split into two parts to better
optimize the runtime.  The helper script, libtool-fix-la, is created when
USE_LIBTOOL is defined.

Lastly, instead of attaching all of the buildlink2 targets to
"pre-configure", they are now attached to "do-buildlink" so that they will
be called regardless of whether NO_CONFIGURE is defined or not.
* Split the libtool script into a main script and a helper script.  The
  helper script is separated to prevent parsing until its needed.  Also
  specially handle the --mode=install case for libtool as we don't really
  care to cache the arguments in those cases.

* Use a more correct strategy for properly quoting and caching arguments
  in the wrapper scripts.  This fixes building php4, kdelibs2, and imlib.