re-add cling variant

[h-vetinari]

It's been quite a while since there have been cling builds on this feedstock (v9!)

clangdev-feedstock/recipe/meta.yaml

Lines 30 to 33 in 95bb844

	# Taken from cloning http://root.cern/git/clang.git and running
	# git show origin/ROOT-patches --quiet -> c43832868861f1fad029e29246381dd427a7dcd8
	# git format-patch cc54f73e76332c635d97a53b5ec369901173be53~1..c43832868861f1fad029e29246381dd427a7dcd8
	- patches/root/0001-Temporary-parsers-should-not-manipulate-global-parse.patch # [variant and variant.startswith("root_")]

In the meantime, cling has started publishing releases again (after an almost 3 year break) following 0.9. There's a bunch of packages depending on this, notably the cppyy* packages (which have also fallen quite a bit behind their pypi upstreams). So I thought we might give this a shot. The patches are taken 1:1 from https://github.com/root-project/llvm-project/commits/cling-llvm18

Please let me know what you think @conda-forge/clangdev @conda-forge/cling @conda-forge/root @conda-forge/cppyy

PS. The last cling builds were for linux-64, osx-64, win-64, but for now I'm attempting to build all targets (not least for the dependents); will pare this back if a platform ends up not being buildable with reasonable effort.

[conda-forge-admin]

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/meta.yaml) and found it was in an excellent condition.

I do have some suggestions for making it better though...

For recipe/meta.yaml:

• ℹ️ The recipe is not parsable by parser conda-souschef (grayskull). This parser is not currently used by conda-forge, but may be in the future. We are collecting information to see which recipes are compatible with grayskull.
• ℹ️ The recipe is not parsable by parser conda-recipe-manager. The recipe can only be automatically migrated to the new v1 format if it is parseable by conda-recipe-manager.

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