In commit "use export all symbols on cygwin" (2003-01-21) we started
passing -Wl,--export-all-symbols when linking shared libraries. Now
cygwin exports all symbols automatically if no symbols are explicitly
exported. When symbols are explicitly exported we want to honor that
narrow interface. Therefore this flag should not be passed.
Change based on patch from issue #10122.
The variable should contain the name of a library needed to link the
symbol equivalent to dlopen. On Cygwin no special library is needed,
and certainly not "gdi32".
Change based on patch from issue #10122.
This moves GNU compiler flags into new-style modules
Compiler/GNU-<lang>.cmake
Platform/<os>-GNU-<lang>.cmake
We use language-independent helper modules
Compiler/GNU.cmake
Platform/<os>-GNU.cmake
to define macros consolidating the information.