Instead of only doing a naive filesystem search, also run the linker
so that it can tell us whether the -F path specified actually contains
the framework we're looking for.
Unfortunately, `extraframework` searching is still not 100% correct in
the case when since we want to search in either /Library/Frameworks or
in /System/Library/Frameworks but not in both. The -Z flag disables
searching in those prefixes and would in theory allow this, but then
you cannot force the linker to look in those by manually adding -F
args, so that doesn't work.
All dependencies were using find_library, has_header, get_define, etc on
self.compiler assuming that it's a compiler that outputs and consumes
C-like libraries. This is not true for D (and in the future, for Rust)
since although they can consume C libraries, they do not use the
C ecosystem.
For such purposes, we now have self.clib_compiler. Nothing uses
self.compiler anymore as a result, and it has been removed.
This class now consolidates a lot of the logic that each external
dependency was duplicating in its class definition.
All external dependencies now set:
* self.version
* self.compile_args and self.link_args
* self.is_found (if found)
* self.sources
* etc
And the abstract ExternalDependency class defines the methods that
will fetch those properties. Some classes still override that for
various reasons, but those should also be migrated to properties as
far as possible.
Next step is to consolidate and standardize the way in which we call
'configuration binaries' such as sdl2-config, llvm-config, pkg-config,
etc. Currently each class has to duplicate code involved with that
even though the format is very similar.
Currently only pkg-config supports multiple version requirements, and
some classes don't even properly check the version requirement. That
will also become easier now.
Jussi Pakkanen
Michael Hirsch, Ph.D
Nirbheek Chauhan
Jon Turney
Elliott Sales de Andrade