Suppress unused variable warning in helper_thread.c #886

Job	Run time
build (linux-gcc)	13m 58s
build (linux-clang)	11m 44s
build (macos)	11m 51s
build (linux-i686-gcc)	13m 1s
build (android)	37s
build (windows-cygwin-64)	15m 22s
build (windows-cygwin-32)	15m 20s
build (windows-msys2-64)	13m 22s
build (android-recovery, ubuntu-22.04, aarch64-linux-android32)	36s
	1h 35m 51s

Provide feedback