[llvm] [libsycl] Add liboffload context handler to default context (PR #213249)

[Sergey Semenov via llvm-commits]

================
@@ -13,15 +13,46 @@ _LIBSYCL_BEGIN_NAMESPACE_SYCL
 
 namespace detail {
 
+ContextImpl::ContextImpl(std::vector<DeviceImpl *> &&DeviceList,
+                         const async_handler &AsyncHandler,
+                         const property_list &PropList, Private)
+    : MAsyncHandler(AsyncHandler), MDevices(DeviceList) {
+  (void)PropList;
+
+  assert(!MDevices.empty() && "Device list must not be empty");
+  const PlatformImpl &RefPlatform = MDevices[0]->getPlatformImpl();
+
+  std::vector<ol_device_handle_t> DeviceIds;
+  DeviceIds.reserve(MDevices.size());
+  for (DeviceImpl *D : MDevices) {
+    assert(D && "Device list must not contain null entries");
+    if (D->getPlatformImpl().getOLHandleRef() != RefPlatform.getOLHandleRef())
+      throw exception(
+          make_error_code(errc::invalid),
+          "Can't add devices across platforms to a single context.");
----------------
sergey-semenov wrote:

```suggestion
          "Can't add devices from multiple platforms to a single context.");
```
Nit

https://github.com/llvm/llvm-project/pull/213249