[LLD][Cygwin] Add libcygwin and libmsys-2.0 to exclude-from-auto-export library list

Linking for Cygwin target always needs -lcygwin (and, -lmsys-2.0
instead for MSYS2 target) but should not auto-export from
them, same as -lmingw32 for MinGW target.

Author: kikairoya

lld/COFF/MinGW.cpp

@@ -46,6 +46,8 @@ AutoExporter::AutoExporter(
       "libclang_rt.profile-arm",
       "libclang_rt.profile-i386",
       "libclang_rt.profile-x86_64",
+      "libcygwin",
+      "libmsys-2.0",
       "libc++",
       "libc++abi",
       "libflang_rt.runtime",