[llvm] [Offload] Add check-offload-unit for liboffload unittests (PR #137312)

[Joseph Huber via llvm-commits]

================
@@ -65,6 +65,13 @@ ol_device_handle_t TestEnvironment::getDevice() {
   static ol_device_handle_t Device = nullptr;
 
   if (!Device) {
+    if (const char *EnvStr = getenv("OFFLOAD_UNITTEST_PLATFORM")) {
----------------
jhuber6 wrote:

Shouldn't we just be able to loop over all the discovered platforms? Most of this stuff is intended to be generic after all.

https://github.com/llvm/llvm-project/pull/137312