Disable all new tests on Windows.

We have language features that depends on swift_in_compiler. Any
platform that does not support this build feature does not really
support the language, so we must continue to disable tests.

Author: atrick

test/SILOptimizer/borrow_introducer_unit.sil

@@ -1,4 +1,6 @@
 // RUN: %target-sil-opt -test-runner %s -o /dev/null 2>&1 | %FileCheck %s
+//
+// REQUIRES: swift_in_compiler
 
 sil_stage raw
 

test/SILOptimizer/enclosing_def_unit.sil

@@ -1,4 +1,6 @@
 // RUN: %target-sil-opt -test-runner %s -o /dev/null 2>&1 | %FileCheck %s
+//
+// REQUIRES: swift_in_compiler
 
 sil_stage raw
 

test/SILOptimizer/ownership_liveness_unit.sil

@@ -4,6 +4,8 @@
 // then consider moving all tests with 'unreachable' into a separate file with the flag
 // -disable-ownership-verification
 
+// REQUIRES: swift_in_compiler
+
 sil_stage canonical
 
 import Builtin