Check for prefixed ar, readelf, and nm

Sometimes with cross-compile toolchains, the tools are prefixed with the
target arch. Using AC_CHECK_TOOL looks for tools named like this.

Signed-off-by: Michael Forney <mforney@mforney.org>
Signed-off-by: Mark Wielaard <mjw@redhat.com>
diff --git a/libdw/ChangeLog b/libdw/ChangeLog
index 3fa6c0e..7a768fc 100644
--- a/libdw/ChangeLog
+++ b/libdw/ChangeLog
@@ -1,3 +1,7 @@
+2013-11-01  Michael Forney  <mforney@mforney.org>
+
+	* Makefile.am: Use READELF.
+
 2013-10-30  Jan Kratochvil  <jan.kratochvil@redhat.com>
 
 	* libdw.map (ELFUTILS_0.158): New.