[LLD][COFF] add __{data,bss}_{start,end}__ symbols for Cygwin support (#136180)
Cygwin requires these symbols for its fork emulation to know what data
to copy into the child. GNU ld defines these symbols for MinGW targets
also, so do the same here.
Cygwin also has the `.data_cygwin_nocopy` section, which is merged into
`.data` outside the `__data_start__` to `__data_end__` range. This
excludes it from fork's copying. AFAIK it's only used by the Cygwin DLL
itself (which requires a custom linker script to link, that's not
supported by LLD), but the section is included in GNU ld's default
linker script so handle it here too.
Signed-off-by: Jeremy Drake <github@jdrake.com>
llvm-project
f66f2fe0 - [LLD][COFF] add __{data,bss}_{start,end}__ symbols for Cygwin support (#136180)
