cmake and make using same env with CC and CXX (#258)
Each "run:" call gets a new environment.
With this, the first "run:" is exporting CC and CXX.
In this "run:" the cmake stuff is created.
The next "run:" to make, is using the default CC and CXX, which is
GCC instead of clang.
And then some of the stuff is build with clang other with gcc
* moved cmake, make and running tests in one "run:" command, so they
are sharing the same environment
* fixed indention
* renamed the name to Build and run
* Build build-clang-9-Linux and build-clang-10-osx are similar now.
Co-authored-by: finger42 <finger42>
