refactor(sycl): do not override CMAKE_CXX_COMPILER

Spack injects its own compiler wrappers which rpath shared libraries
for us and also any user defined flags. Therefore we do not want to
set the compiler in this scenario.

src/sycl/fasten.hpp

@@ -233,6 +233,7 @@ template <size_t PPWI> class IMPL_CLS final : public Bude<PPWI> {
     queue.submit([&](sycl::handler &h) { h.copy(energies.get_access<R>(h), sample.energies.data()); });
     queue.wait_and_throw();
     auto deviceToHostEnd = now();
+
     sample.deviceToHost = {deviceToHostStart, deviceToHostEnd};
 
     return sample;

src/sycl/model.cmake

@@ -1,4 +1,3 @@
-
 register_flag_optional(CMAKE_CXX_COMPILER
         "Any CXX compiler that is supported by CMake detection, this is used for host compilation when required by the SYCL compiler"
         "c++")
@@ -60,18 +59,12 @@ macro(setup)
         set(COMPUTECPP_USER_FLAGS -O3 -no-serial-memop)
 
     elseif (${SYCL_COMPILER} STREQUAL "DPCPP")
-        set(CMAKE_CXX_COMPILER ${SYCL_COMPILER_DIR}/bin/clang++)
-        include_directories(${SYCL_COMPILER_DIR}/include/sycl)
         register_append_cxx_flags(ANY -fsycl)
         register_append_link_flags(-fsycl)
     elseif (${SYCL_COMPILER} STREQUAL "ONEAPI-ICPX")
-        set(CMAKE_CXX_COMPILER icpx)
-        set(CMAKE_C_COMPILER icx)
         register_append_cxx_flags(ANY -fsycl)
         register_append_link_flags(-fsycl)
     elseif (${SYCL_COMPILER} STREQUAL "ONEAPI-Clang")
-        set(CMAKE_CXX_COMPILER clang++)
-        set(CMAKE_C_COMPILER clang)
         register_append_cxx_flags(ANY -fsycl)
         register_append_link_flags(-fsycl)
     else ()