[test] Enable impossible to support test POSIXErrorCode.

The REQUIRES written one in each line were impossible to satisfy in any
platform, so the test wasn't running at all. This was changed to a
REQUIRE-ANY listing all the platforms (and adding Android). I also
needed to add runAllTest() at the end to make the test pass.

Author: drodriguez

validation-test/stdlib/POSIXErrorCode.swift

@@ -1,12 +1,7 @@
 // RUN: %target-run-simple-swift
 // REQUIRES: executable_test
 //
-// REQUIRES: OS=macosx
-// REQUIRES: OS=ios
-// REQUIRES: OS=tvos
-// REQUIRES: OS=watchos
-// REQUIRES: OS=linux-androideabi
-// REQUIRES: OS=linux-gnu
+// REQUIRES-ANY: OS=macosx, OS=ios, OS=tvos, OS=watchos, OS=linux-androideabi, OS=linux-android, OS=linux-gnu
 
 import Swift
 import StdlibUnittest
@@ -163,3 +158,5 @@ POSIXErrorCodeTestSuite.test("Linux POSIX error codes constants") {
 }
 
 #endif
+
+runAllTests()