osdep: Create qemu_getauxval and qemu_init_auxval

Abstract away dependence on a system implementation of getauxval.

Signed-off-by: Richard Henderson <rth@twiddle.net>
diff --git a/util/Makefile.objs b/util/Makefile.objs
index 2bb13a2..af3e5cb 100644
--- a/util/Makefile.objs
+++ b/util/Makefile.objs
@@ -12,3 +12,4 @@
 util-obj-y += hexdump.o
 util-obj-y += crc32c.o
 util-obj-y += throttle.o
+util-obj-y += getauxval.o