Fix compilation on Pop!_OS 22.04 LTS CUDA

Downgrade the C++ version from 17 to 14, and also update the code to remove compilation warnings.

Author: mika314

ggml/CMakeLists.txt

@@ -219,7 +219,11 @@ option(GGML_BUILD_EXAMPLES "ggml: build examples" ${GGML_STANDALONE})
 set(CMAKE_C_STANDARD 11)
 set(CMAKE_C_STANDARD_REQUIRED true)
 
-set(CMAKE_CXX_STANDARD 17)
+if (GGML_SYCL)
+    set(CMAKE_CXX_STANDARD 17)
+else()
+    set(CMAKE_CXX_STANDARD 14)
+endif()
 set(CMAKE_CXX_STANDARD_REQUIRED true)
 
 set(THREADS_PREFER_PTHREAD_FLAG ON)