The current builds fail because without a valid modulemap the setresuid test
failed during configuration time.

Signed-off-by: Vassil Vassilev <vvasilev@cern.ch>

The old contents still had the escaped newlines for the bash command in it.
This also fixes the formatting of the modulemap.

Signed-off-by: Vassil Vassilev <vvasilev@cern.ch>

It seems that execvp can't handle such longs args on the build nodes and
fails when we call `echo $ARGS >> modulemap`.

We now first write this to a file and then append it to the actual
modulemap.

Signed-off-by: Vassil Vassilev <vvasilev@cern.ch>

We use a dummy map during configuration to pass the CMake compiler steps
with the enabled modulemap overlay. We later configure this overlay file
correctly to actually use the STL modulemap.

This reverts commit 5c076c6c.

This reverts commit b406328d, reversing
changes made to 318c7a47.

rootcling now links against libRIO, libCore, libCling.
Any symbol from llvm/clang must now be resolved from within libCling.
libCling thus exports only ROOT_rootcling_Driver and CreateInterpreter().
This will allow to fix the symbol visibility inconsistency.
And it reduces link time.

Our two build systems can generate almost entirely a modulemap file laying out
one module per library. Due to some non-modular implementation in ROOT's core we
still need to treat some header files specially.

This patch appends modular header files to the modulemap while skipping the
predefined ones. Configure-make relates all headers that are installed in
$ROOTSYS/include to their library whereas relates only headers which are part of
library's dictionary.

This reverts commit cb662602.

rootcling version is tied to our internal version of clang. Passing in -fmodules
would use the modules already built from the outside compiler, whose version
might differ. The module files are not compatible among the clang versions.

Allow rootcling to use the modules-specific build flags.

Do not install etc/cmake when building with CMake. The user needs to use the generated ROOTConfig.cmake.

 - bin/pq2
 - bin/rootd
 - bin/xpdtest
 - initd and xinitd start-up scripts
 - don't install some private headers

Improved the FindPCRE.cmake to not rely on pare-config command and looking for directly the header and library.