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* Clang is now supported alternative to GCC
* Remove export of CC and CXX variables for macOS

This makes the source code compatible to Clang.

Adapt CI pipeline to 7 multi core CPUs

See merge request !49

Resolve "Add job for building and deploying DORiE Docker image"

Closes #56

See merge request !47

* setup:dune-env only executes for 'Run pipeline' trigger
* prep:update-dune only runs for master and tags
* deploy jobs only run for master and tags
* split deploy jobs into two cases for master and tags, respectively

* setup job builds and uploads DUNE environment image
* deploy job builds and uploads DORiE image

Use new CI tags

See merge request !48

Resolve "PkLocalFiniteElementMap creates continuous function space"

Closes #67

See merge request !46

[ci skip]

Test affected:
* mass_conservation
* ode_linear_interpolator

Add meta-task issue template from Utopia

See merge request !45

Add changelog task to mr template

See merge request !44

Nonconformity to output

See merge request !43

Resolve "Top-level CMake file got messed up"

Closes #60

See merge request !42