Add awk program check and use which one is found

Change-Id: Ia5ab161f83640189350ebe3a53d46834ea8bf9fc
Signed-off-by: Matthew Barth <msbarth@us.ibm.com>
diff --git a/Makefile.am b/Makefile.am
index 3aa8cf8..70b4895 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -31,6 +31,6 @@
 
 uninstall-hook:
 	cat ${top_builddir}/python_install.log \
-	| awk '{print "$(DESTDIR)"$$1}' | xargs rm -fv
+	| $(AWK) '{print "$(DESTDIR)"$$1}' | xargs rm -fv
 
 endif