Handling of compiler flags

[Linus Seelinger]

I have found that, for example

set(CMAKE_CXX_FLAGS_RELEASE  "-O3 -msse4 -mavx")

in SetupCompiler.cmake can cause serious issues when combining muq with other codes. (For example, Eigen’s vectorization strategy is not compatible with non-vectorized user codes, or some of muq’s options don’t play well with DUNE).

I think in general we should set as few compiler flags as possible, and allow users to pass optimizations etc. from the outside. -Wall and friends could be enforced by CI for example. This should make muq’s behaviour more transparent and allow for better compatibility with e.g. model codes.

@Matthew Parno , Andy, what do you think about this?

[Matthew Parno]

I agree that we should add as few flags as possible.

[Matthew Parno]

Compiler flags were simplified in commit 564c259