[vm/win] Use wide-character api for local hostname on Windows.

Fixes #52701
TEST=test locally

Change-Id: Ia38b67cadea3d15824b06d0a2fc69f0c20192bb6
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/310481
Commit-Queue: Alexander Aprelev <[email protected]>
Reviewed-by: Ryan Macnak <[email protected]>

Author: aam

runtime/bin/platform_win.cc

@@ -218,7 +218,14 @@ bool Platform::LocalHostname(char* buffer, intptr_t buffer_length) {
   if (!SocketBase::Initialize()) {
     return false;
   }
-  return gethostname(buffer, buffer_length) == 0;
+  // 256 is max length per https://learn.microsoft.com/en-us/windows/win32/api/winsock2/nf-winsock2-gethostnamew#remarks
+  const int HOSTNAME_MAXLENGTH = 256;
+  wchar_t hostname_w[HOSTNAME_MAXLENGTH];
+  if (GetHostNameW(hostname_w, HOSTNAME_MAXLENGTH) != 0) {
+    return false;
+  }
+  return WideCharToMultiByte(CP_UTF8, 0, hostname_w, -1, buffer, buffer_length,
+                             nullptr, nullptr) != 0;
 #endif
 }