Migrate to Jinja2 compiler syntax

[regro-cf-autotick-bot]

List of changes done to the recipe: Renamed build with host Moving posix from host to build Removing {{native}}toolchain in favour of compiler() Removing gcc in favour of compiler() Removing libgcc in favour of compiler() Removing pinnings for icu to use values from conda_build_config.yaml. If you need the pin see here for details. Adding C compiler with mingw for windows Adding C++ compiler with mingw for windows Adding merge_build_host: True # [win]

If you have recived a Migrate to Jinja2 compiler syntax PR from me recently please close that one and use this one. It is very likely that this feedstock is in need of migration. Notes and instructions for merging this PR:

1. Please merge the PR only after the tests have passed.
2. Feel free to push to the bot's branch to update this PR if needed.
3. If this recipe has a cython dependency please note that only a C compiler has been added. If the project also needs a C++ compiler please add it by adding - { compiler('cxx') } to the build section

_{This PR was created by the cf-regro-autotick-bot. The cf-regro-autotick-bot is a service to automatically track the dependency graph, migrate packages, and propose package version updates for conda-forge. If you would like a local version of this bot, you might consider using rever. Rever is a tool for automating software releases and forms the backbone of the bot's conda-forge PRing capability. Rever is both conda (conda install -c conda-forge rever) and pip (pip install re-ver) installable. Finally, feel free to drop us a line if there are any issues!}

[conda-forge-linter]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipe) and found it was in an excellent condition.