This is the convention suggested in the Sphinx documentation and is
already used in several other places in the CMake documentation.
Update a few places where we were using other characters.
Explain how to use $<BUILD_INTERFACE> and $<INSTALL_INTERFACE> directly
in the documentation of the target_include_directories command and
INTERFACE_INCLUDE_DIRECTORIES target property. Otherwise readers need
to notice the link to the cmake-buildsystem(7) manual and find the
example in that to understand the need for these expressions.
Also fix the explanation in cmake-buildsystem(7) to not claim that
relative paths may be used inside a BUILD_INTERFACE expression.
People will be tempted to put things there for convenience, thereby
causing conflicts similar to
http://thread.gmane.org/gmane.comp.compilers.clang.devel/35162/focus=35169
where it is conceivable that the LLVM developers could put a flag on
a target for convenience, which would cause conflicts for some downstreams.
Describe how to define a buildsystem of binary targets, how to
express dependencies between them, how to add build specifications,
how to specify usage requirements, transitive and compatible
propagation and the various pseudo targets.
Brad King
Stephen Kelly