Remove unnecessary -lm

src/Makefile

@@ -4,7 +4,7 @@ CFLAGS += -fPIC
 all: $(TARGETS)
 
 radangel: radangel.o
-	$(CC) -std=gnu99 -Wall $(LDFLAGS) $^ -pthread -lm -lhidapi-libusb -o $@
+	$(CC) -std=gnu99 -Wall $(LDFLAGS) $^ -pthread -lhidapi-libusb -o $@
 
 radangel.o: radangel.c