Make libelf warnings quiet.

The clang -Wtautological-compare compare ones are especially annoying.

lib/Makefile.in

@@ -37,7 +37,7 @@ libelf_notice:
 	@echo "[*] Building libelf"
 
 $(top_srcdir)/lib/libelf/lib/libelf.a: libelf_notice
-	+@cd libelf/lib && $(MAKE) libelf.a
+	+@cd libelf/lib && $(MAKE) CFLAGS="-g -O2 -w" libelf.a
 
 libelf: @LIBELF_BUNDLED@