graphics/libjxl: unbreak on riscv64 after 32c2b95c

Hard-float 'd' ABI can't be used for a target that doesn't support the D instruction set extension (ignoring target-abi)
ld: error: too many errors emitted, stopping now (use -error-limit=0 to see all errors)
c++: error: linker command failed with exit code 1 (use -v to see invocation)

Reported by:	pkg-fallout