[lld] [LLD][COFF] add __{data,bss}_{start,end}__ symbols for Cygwin support (PR #136180)

[via llvm-commits]

================
@@ -2039,6 +2039,7 @@ void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
     parseMerge(".ctors=.rdata");
     parseMerge(".dtors=.rdata");
     parseMerge(".CRT=.rdata");
+    parseMerge(".data_cygwin_nocopy=.data");
----------------
jeremyd2019 wrote:

no, it makes sense to test `.data_cygwin_nocopy` along with `__data_start__` and `__data_end__`, because the whole point of it is that it is outside (after) those symbols.

https://github.com/llvm/llvm-project/pull/136180