- use absolute path for top_builddir and top_srcdir.
  Fixes make trying to include the very same file in an endless loop.
diff --git a/libbb/Makefile b/libbb/Makefile
index 6e6a398..1d4f547 100644
--- a/libbb/Makefile
+++ b/libbb/Makefile
@@ -4,8 +4,12 @@
 #
 # Licensed under the GPL v2, see the file LICENSE in this tarball.
 
+ifndef top_srcdir
 top_srcdir=..
+endif
+ifndef top_builddir
 top_builddir=..
+endif
 srcdir=$(top_srcdir)/libbb
 LIBBB_DIR:=./
 include $(top_builddir)/Rules.mak