Feature: support OSX frameworks

[SSE4]

Changelog: Feature: Better support OSX frameworks by declaring cppinfo.frameworks.
Docs: conan-io/docs#1414

closes: #5245

part 1
extend CppInfo and DepsCppInfo classes to support frameworks and framework_paths properties.
right now many of bincrafters recipes have the following code to manage frameworks:

def package_info(self):
    ...
    frameworks = ['CoreVideo', 'CoreMedia', 'CoreGraphics', 'CoreFoundation', 'OpenGL', 'Foundation']
    for framework in frameworks:
        self.cpp_info.exelinkflags.append("-framework %s" % framework)
    self.cpp_info.sharedlinkflags = self.cpp_info.exelinkflags

so, frameworks are currently managed with exelinkflags/sharedlinkflags, which is kinda ugly. proposed changes allow to write just something like:
by default, self.cpp_info.framework_paths includes rootpath, not sure if it's wise choice, need to check where frameworks are usually installed by conventions (bin vs lib vs Frameworks vs root)

def package_info(self):
    ...
    self.cpp_info.frameworks = ['CoreVideo', 'CoreMedia', 'CoreGraphics', 'CoreFoundation', 'OpenGL', 'Foundation']

part 2
set DYLD_FRAMEWORK_PATH in RunEnvironment and ConanFile.run, similar to how DYLD_LIBRARY_PATH is currently set. see https://www.manpagez.com/man/1/dyld/ for the details.

part 3
use frameworks and framework_paths in generators. right now implemented only in cmake generator via find_library - frameworks found are appended to the CONAN_LIBS.

changes were tested on SFML branch: https://github.com/bincrafters/conan-sfml/compare/framework/2.5.1?expand=1, which allows to compile frameworks instead of regular libraries via options: -o sfml:shared=True -o sfml:framework=True. as result, it creates two frameworks: SFML.framework and sfml-system.framework.

TODO:

• write some tests

• decide which directories should be used by default in self.cpp_info.framework_paths

• implement other generators (probably, xcode, compiler_args, virtualenv/virtualrunenv, other cmake_* generators)

• check if we have to change something about editable mode in case of frameworks?

• Refer to the issue that supports this Pull Request.

• If the issue has missing info, explain the purpose/use case/pain/need that covers this Pull Request.

• I've read the Contributing guide.

• I've followed the PEP8 style guides for Python code.

• I've opened another PR in the Conan docs repo to the develop branch, documenting this one.

^{Note: By default this PR will skip the slower tests and will use a limited set of python versions. Check here how to increase the testing level by writing some tags in the current PR body text.}

[SSE4]

@jgsogo please take a look at the proposal and lemme know what do you think

[jgsogo]

I know nothing about apple frameworks 😞 . If this is going for the next release (cc @lasote) I need to have a look at it almost from scratch, right now I can only say that it looks like promising.

[jgsogo]

Can you fix the failing test, @SSE4? As the issue is tagged for v1.19, let's try to push this PR forward

[SSE4]

@jgsogo yeah, I am planning to add tests, but before going too deep, I want some feedback, if it's a right direction to go or not

[lasote]

In general, I think the idea is ok. The default root dir I don't think is a good choice. We have seen for c3i that it is difficult to check if a package is built correctly without a well know folder structure. I don't know which one is the best, but we could enforce a new one if needed (convention).

Please add tests, make a proposition for the default folder and specify which other generators are you going to adapt for the apple frameworks (if any)

[SSE4]

yeah, I think:

1. I'll use Frameworks as a default frameworks root directory
2. I'll use the following generators for the start cmake*, pkg-config, xcode, compiler-flags, virtual*env

[SSE4]

@jgsogo @lasote
changes are ready for the review now:

1. tests were added
2. supported generators so far: json, compiler_args, xcode, cmake, cmake-multi, pkg-config, txt
3. CppInfo and DepsCppInfo now have frameworks and framework_paths attributes
4. DYLD_FRAMEWORK_PATH is now set by RunEnvironment (and virtualrunenv)
5. default framework directory is Frameworks

[SSE4]

just removed WIP title, as it was confusing

[lasote]

@SSE4 Write and link the docs ASAP. It really helps to understand the PR (and it is needed to complete a feature)

[SSE4]

@lasote docs added

[lasote]

Looking good, some important comments

[lasote]

Add a test for find package

[SSE4]

@lasote added cmake_find_package_frameworks_test