feat: add cygwin support

Author: Berrysoft

src/os/unix/consts.rs

@@ -88,6 +88,7 @@ mod posix {
             target_os = "redox",
             target_os = "nto",
             target_os = "hurd",
+            target_os = "cygwin",
         ))] {
             pub(super) const RTLD_LAZY: c_int = 1;
         } else {
@@ -127,6 +128,7 @@ mod posix {
             target_os = "redox",
             target_os = "nto",
             target_os = "hurd",
+            target_os = "cygwin",
         ))] {
             pub(super) const RTLD_NOW: c_int = 2;
         } else if #[cfg(all(target_os = "android",target_pointer_width = "32"))] {
@@ -179,6 +181,7 @@ mod posix {
             target_os = "redox",
             target_os = "nto",
             target_os = "hurd",
+            target_os = "cygwin",
         ))] {
             pub(super) const RTLD_GLOBAL: c_int = 0x100;
         } else {
@@ -224,6 +227,7 @@ mod posix {
             target_os = "fuchsia",
             target_os = "redox",
             target_os = "hurd",
+            target_os = "cygwin",
         ))] {
             pub(super) const RTLD_LOCAL: c_int = 0;
         } else {