We remove the shared library compile/link flags "-fPIC" and "-shared"
because they are not provided by all compilers on Linux. This allows us
to drop code from the Linux-XL-*.cmake files that erases the bad flags.
All other supported compilers already provide their correct flags for
Linux in their own platform information files.
This is a GNU-specific option that should not be specified for all
compilers on Linux. It tells the GNU compiler to pass -export-dynamic
to the linker to export symbols from executables for use by plugins.
Since we provide the ENABLE_EXPORTS target property to do the same thing
in a cross-platform way, there is no need to pass -rdynamic always.
Since the option is not useful for GNU tools and breaks other tools on
Linux we simply remove it from CMAKE_SHARED_LIBRARY_LINK_<lang>_FLAGS.
This also allows us to stop setting the variable in other Linux compiler
files just to erase the bad flag.
See issue #9985.
In Platform/Linux.cmake we add GNU flags as default for the platform
which breaks non-GNU compilers. Later we should refactor these flag
files to put compiler-specific flags only in files loaded for each
compiler. Until then this commit fixes the XL C++ compiler flags on
Linux by erasing the GNU flags. See issue #9469.
