Build: DPCPP, don't build tests as they are not needed

They also try to use explicitly disabled libraries, so it also leads to
build failures.

build_files/build_environment/cmake/dpcpp.cmake

@@ -50,6 +50,7 @@ set(DPCPP_EXTRA_ARGS
   -DUMF_DISABLE_HWLOC=ON
   -DUMF_BUILD_SHARED_LIBRARY=OFF
   -DSYCL_ENABLE_XPTI_TRACING=OFF
+  -DSYCL_INCLUDE_TESTS=OFF
   -DUR_ENABLE_TRACING=OFF
   -DUR_BUILD_TOOLS=OFF
   # Below here is copied from an invocation of buildbot/config.py
@@ -68,7 +69,6 @@ set(DPCPP_EXTRA_ARGS
   -DSYCL_BUILD_PI_HIP_PLATFORM=AMD
   -DLLVM_BUILD_TOOLS=ON
   -DSYCL_ENABLE_WERROR=OFF
-  -DSYCL_INCLUDE_TESTS=ON
   -DLLVM_ENABLE_DOXYGEN=OFF
   -DLLVM_ENABLE_SPHINX=OFF
   -DBUILD_SHARED_LIBS=OFF