b87804c2ba
In the gcc-riscv compiler, __builtin_ffs will call ffs, and calling __builtin_ffs in ffs will cause recursion Change ffs to an inline function, and compile ffs implemented by nuttx by default. Only call the implementation of nuttx when the compiler cannot provide an ffs implementation. Signed-off-by: yinshengkai <yinshengkai@xiaomi.com>