Conan

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- Bugfix: Fix link order with private requirements.
- Bugfix: Removed duplicate `-std` flag in CMake < 3 or when the standard is not yet supported by `CMAKE_CXX_STANDARD`.
- Bugfix: Check `scm` attribute to avoid breaking recipes with already defined one.
- Feature: Conan workspaces.

- Bugfix: Added system libraries to the `cmake_find_package` generator.
- Fix: Added SIGTERM signal handler to quit safely.
- Bugfix: Fixed miss-detection of `gcc 1` when no gcc was on a Linux machine.

===

Bugfix: Fixed multi-config packages 2981
Bugfix: Fixed `cppstd` management with CMake and 20 standard.

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- Bugfix: Solved issue with symlinks making recipes to fail with `self.copy`.
- Bugfix: Fixed c++20 standard usage with modern compilers and the creation of the ``settings.yml`` containing the settings values.
- Bugfix: Fixed error with cased directory names in Windows.
- BugFix: Modified confusing warning message in the SCM tool when the remote couldn't be detected.

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- Feature: Added scm conanfile attribute, to easily clone/checkout from remote repositories and to capture the remote and commit in the exported recipe when the recipe and the sources lives in the same repository.
- Feature: Added ``cmake_paths`` generator to create a file setting ``CMAKE_MODULE_PATH`` and ``CMAKE_PREFIX_PATH`` to the packages folders.
It can be used as a CMake toolchain to perform a transparent CMake usage, without include any line of cmake code related to Conan.
- Feature: Added ``cmake_find_package`` generator that generates one ``FindXXX.cmake`` file per each dependency both with classic CMake approach and modern
using transitive CMake targets. Read more :ref:`here <cmake_find_package_generator>`.
- Feature: Added :command:`conan search --json` json output to the command.
- Feature: CMake build helper now sets ``PKG_CONFIG_PATH`` automatically and receives new parameter ``pkg_config_paths`` to override it.
- Feature: CMake build helper doesn't require to specify "arch" nor "compiler" anymore when the generator is "Unix Makefiles".
- Feature: Introduced default settings for GCC 8, Clang 7.
- Feature: Introduced support for c++ language standard c++20.
- Feature: Auto-managed ``fPIC`` option in AutoTools build helper.
- Feature: ``tools.vcvars_command()`` and ``tools.vcvars_dict()`` now take ``vcvars_ver`` and ``winsdk_version`` as parameters.
- Feature: ``tools.vcvars_dict()`` gets only the env vars set by vcvars with new parameter ``only_diff=True``.
- Feature: Generator ``virtualbuildenv`` now sets Visual Studio env vars via ``tool.vcvars_dict()``.
- Fix: Message "Package '1' created" in package commands with ``short_paths=True`` now shows package ID.
- Fix: ``tools.vcvars_dict()`` failing to create dictionary due to newlines in vcvars command output.
- Bugfix: ``tools.which()`` returning directories instead of only files.
- Bugfix: Inconsistent local cache when developing a recipe with ``short_paths=True``.
- Bugfix: Fixed reusing MSBuild() helper object for multi-configuration packages.
- Bugfix: Fixed authentication using env vars such as ``CONAN_PASSWORD`` when ``CONAN_NON_INTERACTIVE=True``.
- Bugfix: Fixed Android api_level was not used to adjust CMAKE_SYSTEM_VERSION.
- Bugfix: Fixed MSBuild() build helper creating empty XML node for runtime when the setting was not declared.
- Bugfix: Fixed ``default_options`` not supporting ``=`` in value when specified as tuple.
- Bugfix: AutoToolsBuildEnvironment build helper's ``pkg_config_paths`` parameter now sets paths relative to the install folder or absolute
ones if provided.

===

- Bugfix: Fixed encoding issues writing to files and calculating md5 sums.