Error handling specific for system with no devices

Setting environment variable `ONEAPI_DEVICE_SELECTOR=cpu` effectively
disables all devices. This PR wraps some calls to DPC++ RT routines
in try/catch to properly handle exceptions that would arise from a call
should the said environment variable be set.

Author: oleksandr-pavlyk

libsyclinterface/source/dpctl_sycl_device_manager.cpp

@@ -208,7 +208,14 @@ DPCTLDeviceMgr_GetDevices(int device_identifier)
     if (!device_identifier)
         return wrap<vecTy>(Devices);
 
-    const auto &root_devices = device::get_devices();
+    std::vector<device> root_devices;
+    try {
+        root_devices = device::get_devices();
+    } catch (std::exception const &e) {
+        delete Devices;
+        error_handler(e, __FILE__, __func__, __LINE__);
+        return nullptr;
+    }
     dpctl_default_selector mRanker;
 
     for (const auto &root_device : root_devices) {

libsyclinterface/source/dpctl_sycl_platform_interface.cpp

@@ -194,7 +194,13 @@ __dpctl_give DPCTLPlatformVectorRef DPCTLPlatform_GetPlatforms()
     using vecTy = std::vector<DPCTLSyclPlatformRef>;
     vecTy *Platforms = nullptr;
 
-    auto platforms = platform::get_platforms();
+    std::vector<platform> platforms;
+    try {
+        platforms = platform::get_platforms();
+    } catch (std::exception const &e) {
+        error_handler(e, __FILE__, __func__, __LINE__);
+        return nullptr;
+    }
 
     try {
         Platforms = new vecTy();