Cleaning up some warnings and enabling -Werror on Intel GPU CI tests #208

Job	Run time
lint	13s
check_docker_files / check_docker_files	6s
build_base	0s
build (openmp, gcc, gcc, g++, -DKokkos_ENABLE_OPENMP=ON, -DCMAKE_CXX_FLAGS="-Wall -Wextra" -DCMAK...	5m 10s
build (threads, gcc, gcc, g++, -DKokkos_ENABLE_THREADS=ON, -DCMAKE_CXX_FLAGS="-Wall -Wextra" -DCM...	5m 44s
build (serial, gcc, gcc, g++, -DKokkos_ENABLE_SERIAL=ON, -DCMAKE_CXX_FLAGS="-Wall -Wextra" -DCMAK...	5m 59s
build (cuda, nvcc, gcc, g++, -DKokkos_ENABLE_CUDA=ON -DKokkos_ARCH_AMPERE80=ON, -DCMAKE_CXX_FLAGS...	13m 25s
build (cuda, nvcc, gcc, g++, -DKokkos_ENABLE_CUDA=ON -DKokkos_ARCH_AMPERE80=ON, -DCMAKE_CXX_FLAGS...	15m 55s
build (hip, rocm, hipcc, hipcc, -DKokkos_ENABLE_HIP=ON -DKokkos_ARCH_VEGA90A=ON, -DCMAKE_CXX_FLAG...	13m 25s
build (hip, rocm, hipcc, hipcc, -DKokkos_ENABLE_HIP=ON -DKokkos_ARCH_VEGA90A=ON, -DCMAKE_CXX_FLAG...	11m 56s
build (rocm, rocm, hipcc, hipcc, -DKokkos_ENABLE_HIP=ON -DKokkos_ARCH_VEGA90A=ON, -DCMAKE_CXX_FLA...	12m 28s
build (rocm, rocm, hipcc, hipcc, -DKokkos_ENABLE_HIP=ON -DKokkos_ARCH_VEGA90A=ON, -DCMAKE_CXX_FLA...	12m 46s
build (sycl, intel, icx, icpx, -DKokkos_ENABLE_SYCL=ON -DKokkos_ARCH_INTEL_GEN=ON, -DCMAKE_CXX_FL...	19m 49s
build (sycl, intel, icx, icpx, -DKokkos_ENABLE_SYCL=ON -DKokkos_ARCH_INTEL_GEN=ON, -DCMAKE_CXX_FL...	20m 54s
test (cuda, nvcc, self-hosted, cuda)	7s
test (openmp, gcc, ubuntu-latest)	23s
test (threads, gcc, ubuntu-latest)	23s
test (serial, gcc, ubuntu-latest)	24s
	2h 19m 7s

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