heyu: fix errors about duplicate symbols with ndk >=r22
Errors looks like:
aarch64-linux-android-clang -fstack-protector-strong -Oz -Drindex=strrchr -L/data/data/com.termux/files/usr/lib -Wl,-rpath=/data/data/com.termux/files/usr/lib -fopenmp -static-openmp -Wl,--enable-new-dtags -Wl,--as-needed -Wl,-z,relro,-z,now -o heyu date.o erase.o info.o message.o relay.o monitor.o reset.o setclock.o stop.o tty.o x10.o xread.o xwrite.o status.o cm11a.o eeprom.o process.o sun.o cmd.o config.o x10state.o poll.o modules.o cm17a.o xsync.o timing.o cm10a.o tty_aux.o relay_aux.o x10aux.o rfxcom.o digimax.o oregon.o -lm
ld: error: duplicate symbol: newsb
>>> defined at tty.c
>>> tty.o:(newsb)
>>> defined at tty_aux.c
>>> tty_aux.o:(.bss+0x30)
ld: error: duplicate symbol: oldsb
>>> defined at tty.c
>>> tty.o:(oldsb)
>>> defined at tty_aux.c
>>> tty_aux.o:(.bss+0x0)
ld: error: duplicate symbol: spoolfile
>>> defined at relay.c
>>> relay.o:(spoolfile)
>>> defined at relay_aux.c
>>> relay_aux.o:(.bss+0x1C4)
clang-12: error: linker command failed with exit code 1 (use -v to see invocation)
make[1]: *** [Makefile:467: heyu] Error 1
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