- improve library checks to avoid unnecessary rebuild when
  cross-compiling

- initialise some commonly used variables

- add library function for checking library existence that also
  accounts for windows cross-compilation targets

- may fail to find mpi.h with ThirdParty openmpi

- remove makeAdios1 (ADIOS1 considered defunct for our purposes)

- arguments passed to stripCompilerFlags caused the misbehaviour

- if passed things like "clang-9", strip down to the base name "clang"

- include makeAdios2 into the Allwmake list (as optional component)

- remove old dependency of adios2 on the adios1 library

- in 1906, we changed the handling of compiler flags to include the
  exact values as used by OpenFOAM.

  While this is needed for compiling some external programs -- see
  OpenFOAM-plus#1256
  for the discussion -- it appears to bring in flags that upset
  some of the ParaView (and possibly VTK) compilation.

  The culprits are likely to be found in the various '-W' switches,
  but for now we simply extract a mininal set of compiler flags
  that include -std=c++11 -m64 -fPIC, but no optimization flags,
  additional warnings flags or OpenFOAM-specific defines.

- add links for newest khaip, scotch (untested)

- improve handling of scotch build toolchain

- relax the test for existence of libscotcherrexit, which can also be
  incorporated into libscotch itself

- additional safety when using wmake to generate .so or exe files.
  These third-party libraries must not themselves have a link
  dependency on OpenFOAM.

- bypasses generation of executables

- we do not generally need any of executables, just the libraries.
  This also avoids generating a libscotchmetis too.

- support use of wmake -show-xyz, as well as older WM_CC, WM_CFLAGS etc.

- add support for Makefile.inc for scotch

- add -toolset= option for making boost and use b2 instead of legacy
  bjam for configuration

- still needs more testing to determine the best combination of versions

- note: mpich now builds libmpi.so instead of libmpich.so

- this pulls in the other bits (Module_vtkParallelMPI,
  Module_vtkRenderingParallel, ...)