SYCL: do not skip CPU or FPGA if explicitly selected

It can be useful to be able to use SYCL on CPU
e.g. to run tests on a machine without a GPU.

With this commit a user can enable the use
of the CPU with the following env variable:

export ONEAPI_DEVICE_SELECTOR="opencl:cpu"

Signed-off-by: Salvatore Mesoraca <s.mesoraca16@gmail.com>

ggml/src/ggml-sycl/dpct/helper.hpp

@@ -910,6 +910,7 @@ namespace dpct
             auto platform_list = sycl::platform::get_platforms();
 
             for (const auto& platform : platform_list) {
+                if (!env || !std::strstr(env, "cpu")) {
                     auto devices = platform.get_devices();
                     auto gpu_dev = std::find_if(devices.begin(), devices.end(), [](const sycl::device& d) {
                         return d.is_gpu();
@@ -920,6 +921,7 @@ namespace dpct
                         //      << "] does not contain GPU devices, skipping\n";
                         continue;
                     }
+                }
 
                 auto platform_name = platform.get_info<sycl::info::platform::name>();
                 std::string platform_name_low_case;