cmake: Fix CMake 3.20 CMP0115 warnings.
Policy CMP0115 is not set: Source file extensions must be explicit.
https://cmake.org/cmake/help/v3.20/policy/CMP0115.html
Signed-off-by: Vinson Lee vlee@freedesktop.org
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Policy CMP0115 is not set: Source file extensions must be explicit.
https://cmake.org/cmake/help/v3.20/policy/CMP0115.html
Signed-off-by: Vinson Lee vlee@freedesktop.org