runtime: silence unhelpful warning

This TODO has existed since the introduction of the Windows platform and
has not been addressed. The implementation at this point is well tested
in practice. Clean up the warning message and style and remove the
warning.

Author: compnerd

stdlib/public/stubs/Random.cpp

@@ -62,19 +62,19 @@ void swift_stdlib_random(void *buf, __swift_size_t nbytes) {
 }
 
 #elif defined(_WIN32) && !defined(__CYGWIN__)
-#warning TODO: Test swift_stdlib_random on Windows
 
 SWIFT_RUNTIME_STDLIB_API
 void swift_stdlib_random(void *buf, __swift_size_t nbytes) {
   while (nbytes > 0) {
-    auto actual_nbytes = std::min(nbytes, (__swift_size_t)ULONG_MAX);
+    __swift_size_t actual_nbytes =
+        std::min(nbytes, static_cast<__swift_size_t>(ULONG_MAX));
     NTSTATUS status = BCryptGenRandom(nullptr,
                                       static_cast<PUCHAR>(buf),
                                       static_cast<ULONG>(actual_nbytes),
                                       BCRYPT_USE_SYSTEM_PREFERRED_RNG);
-    if (!BCRYPT_SUCCESS(status)) {
-      fatalError(0, "Fatal error: 0x%lX in '%s'\n", status, __func__);
-    }
+    if (!BCRYPT_SUCCESS(status))
+      fatalError(0, "Fatal error: BCryptGenRandom returned 0x%lX in '%s'\n",
+                 status, __func__);
 
     buf = static_cast<uint8_t *>(buf) + actual_nbytes;
     nbytes -= actual_nbytes;