[test] Test sendability of POSIXErrorCode

Author: glessard

validation-test/stdlib/POSIXErrorCode.swift

@@ -1,4 +1,4 @@
-// RUN: %target-run-simple-swift
+// RUN: %target-run-simple-swift -strict-concurrency=complete
 // REQUIRES: executable_test
 // REQUIRES: VENDOR=apple || OS=linux-androideabi || OS=linux-android || OS=linux-gnu || OS=openbsd || OS=freebsd
 // UNSUPPORTED: freestanding
@@ -18,6 +18,10 @@ import StdlibUnittest
 
 var POSIXErrorCodeTestSuite = TestSuite("POSIXErrorCode")
 
+// Ensure that POSIXErrorCode is actually Sendable
+func send(_ value: some Sendable) {}
+send(POSIXErrorCode.EPERM)
+
 #if canImport(Darwin)
 
 POSIXErrorCodeTestSuite.test("Darwin POSIX error codes constants") {