Fix the braid example.

[drwells]

• Rewrite CMakeLists.txt
• Fix test output

[bangerth]

Well, this does not appear to work:

[ 40%] Building CXX object CMakeFiles/parallel_in_time_lib.dir/src/Utilities.cc.o
/__w/code-gallery/code-gallery/parallel_in_time/src/Utilities.cc:51:13: warning: ‘void openFile()’ defined but not used [-Wunused-function]
   51 | static void openFile()
      |             ^~~~~~~~
/__w/code-gallery/code-gallery/parallel_in_time/src/Utilities.cc:45:13: warning: ‘void setFileName()’ defined but not used [-Wunused-function]
   45 | static void setFileName()
      |             ^~~~~~~~~~~
/__w/code-gallery/code-gallery/parallel_in_time/src/Utilities.cc:17:26: warning: ‘s_pout_open’ defined but not used [-Wunused-variable]
   17 | static bool              s_pout_open = false ;
      |                          ^~~~~~~~~~~
/__w/code-gallery/code-gallery/parallel_in_time/src/Utilities.cc:16:26: warning: ‘s_pout_init’ defined but not used [-Wunused-variable]
   16 | static bool              s_pout_init = false ;
      |                          ^~~~~~~~~~~
[ 60%] Linking CXX shared library libparallel_in_time_lib.so
[ 60%] Built target parallel_in_time_lib
[ 80%] Building CXX object CMakeFiles/parallel_in_time.dir/src/parallel_in_time.cc.o
In file included from /usr/include/deal.II/numerics/vector_tools.h:20,
                 from /__w/code-gallery/code-gallery/parallel_in_time/src/BraidFuncs.hh:18,
                 from /__w/code-gallery/code-gallery/parallel_in_time/src/parallel_in_time.cc:20:
/usr/include/deal.II/base/config.h:540:12: fatal error: mpi.h: No such file or directory
  540 | #  include <mpi.h>
      |            ^~~~~~~
compilation terminated.

[drwells]

I think I fixed it.

[marcfehling]

Testers are happy, so I'll merge :shipit: