fix(flock): check if they are marked unsupported in libstd

Before this Cargo invokes syscalls and check whether it gets ENOTSUP to
determine flock is unsupported. However, now the "unsupported platforms"
are pre-defined by libstd [1]. Cargo should perhaps return unsupported
if a platform is marked unsupported by libstd.

Without this, some people on Termux may be affected I guess?

[1]: e9b6085088/library/std/src/sys/fs/unix.rs (L1395-L1410)

src/cargo/util/flock.rs

@@ -435,13 +435,15 @@ fn error_unsupported(err: &std::io::Error) -> bool {
         #[allow(unreachable_patterns)]
         Some(libc::ENOTSUP | libc::EOPNOTSUPP) => true,
         Some(libc::ENOSYS) => true,
-        _ => false,
+        _ => err.kind() == std::io::ErrorKind::Unsupported,
     }
 }
 
 #[cfg(windows)]
 fn error_unsupported(err: &std::io::Error) -> bool {
     use windows_sys::Win32::Foundation::ERROR_INVALID_FUNCTION;
-    err.raw_os_error()
-        .map_or(false, |x| x == ERROR_INVALID_FUNCTION as i32)
+    match err.raw_os_error() {
+        Some(code) if code == ERROR_INVALID_FUNCTION as i32 => true,
+        _ => err.kind() == std::io::ErrorKind::Unsupported,
+    }
 }