strings: add `ffs` function · phoenix-rtos/libphoenix@6f26731

Build: _build/armv7a9-zynq7000-qemu/busybox/busybox-1.27.2/scripts/basic/split-include.c#L134

ignoring return value of 'fgets' declared with attribute 'warn_unused_result' [-Wunused-result]

Build: _build/armv7a9-zynq7000-qemu/busybox/busybox-1.27.2/scripts/kconfig/conf.c#L106

ignoring return value of 'fgets' declared with attribute 'warn_unused_result' [-Wunused-result]

Build: _build/armv7a9-zynq7000-qemu/busybox/busybox-1.27.2/scripts/kconfig/conf.c#L354

ignoring return value of 'fgets' declared with attribute 'warn_unused_result' [-Wunused-result]

Build: _build/armv7a9-zynq7000-qemu/busybox/busybox-1.27.2/scripts/kconfig/mconf.c#L847

ignoring return value of 'write' declared with attribute 'warn_unused_result' [-Wunused-result]

Build: _build/armv7a9-zynq7000-qemu/busybox/busybox-1.27.2/scripts/kconfig/mconf.c#L481

ignoring return value of 'pipe' declared with attribute 'warn_unused_result' [-Wunused-result]

Build: _build/armv7a9-zynq7000-qemu/busybox/busybox-1.27.2/applets/usage.c#L52

ignoring return value of 'write' declared with attribute 'warn_unused_result' [-Wunused-result]

Build: _build/armv7a9-zynq7000-qemu/busybox/busybox-1.27.2/applets/usage_pod.c#L74

format not a string literal and no format arguments [-Wformat-security]

Build: _build/armv7a9-zynq7000-qemu/busybox/busybox-1.27.2/init/reboot.h#L27

#warning "poweroff unsupported, using halt as fallback" [-Wcpp]

Build: _build/armv7a9-zynq7000-qemu/busybox/busybox-1.27.2/coreutils/stty.c#L288

"CSIZE" is not defined, evaluates to 0 [-Wundef]

Build: _build/armv7a9-zynq7000-qemu/busybox/busybox-1.27.2/loginutils/login.c#L513

variable 'from_getty' set but not used [-Wunused-but-set-variable]

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