cmake: fix setting `CMAKE_HIP_FLAGS` #4547

Job	Run time
Build source distribution	26s
determine-arm64-runner	1s
Build wheels for cp311-manylinux_x86_64	5m 26s
Build wheels for cp311-manylinux_x86_64	5m 31s
Build wheels for cp311-macosx_x86_64	7m 19s
Build wheels for cp311-macosx_arm64	5m 24s
Build wheels for cp311-win_amd64	7m 19s
Build wheels for cp310-manylinux_aarch64	4m 19s
build_docker (12)	3m 1s
build_docker (_cu11, 11)	2m 52s
build_pypi_index	12s
upload_pypi	0s
deploy_pypi_index	0s
Pass testing build wheels	2s
	41m 52s

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