[SYCL] Tests for win_proxy_loader (intel#1465)

Tests to verify win_proxy_loader keeps plugin DLLs from unloading until after piTearDown is complete.

Author: cperkinsintel

SYCL/Basic/buffer/buffer_release.cpp

@@ -1,3 +1,6 @@
+// UNSUPPORTED: windows
+//   DeferredMemory Destruction not presently supported on Windows.
+
 // RUN: %clangxx -fsycl -fsycl-targets=%sycl_triple %s -o %t.out
 // RUN: %CPU_RUN_PLACEHOLDER %t.out
 

SYCL/Plugin/dll-detach-order.cpp

@@ -0,0 +1,12 @@
+// REQUIRES: windows
+// RUN: env SYCL_PI_TRACE=2 sycl-ls | FileCheck %s
+
+// ensure that the plugins are detached AFTER piTearDown is done executing
+
+// CHECK: ---> DLL_PROCESS_DETACH syclx.dll
+// CHECK: ---> piTearDown(
+
+// whatever plugin THIS is
+// CHECK: ---> DLL_PROCESS_DETACH
+
+// CHECK: ---> DLL_PROCESS_DETACH win_proxy_loader.dll

SYCL/Plugin/pi-teardown.cpp

@@ -0,0 +1,4 @@
+// ensure that piTearDown is called
+
+// RUN: env SYCL_PI_TRACE=2 sycl-ls | FileCheck %s
+// CHECK: ---> piTearDown