Fix setting the SIMD target in the djxl_fuzzer. (#349)
Fix setting the SIMD target in the djxl_fuzzer. (#349)

SetSupportedTargetsForTest() expects a target mask, not an index in the
targets array.
libjxl/libjxl,libjxl/libjxl,libjxl/libjxl,libjxl/libjxl,libjxl/libjxl,libjxl/libjxl,libjxl/libjxl,libjxl/libjxl