In-tree this comes out to $(DESTDIR)$(bindir).  Out of tree, for some reason,
it's just $(bindir).  Anyhow, the issue is moot on Gentoo, or even if not, it's
never guile-config/Makefile's job to solve it.

-gmt

diff -urpN guile-1.8.8.orig/guile-config/Makefile.am guile-1.8.8/guile-config/Makefile.am
--- guile-1.8.8.orig/guile-config/Makefile.am	2010-12-13 09:24:39.000000000 -0800
+++ guile-1.8.8/guile-config/Makefile.am	2013-09-30 17:04:50.140720067 -0700
@@ -43,4 +43,5 @@ guile-config: guile-config.in ${top_buil
 ## Get rid of any copies of the configuration script under the old
 ## name, so people don't end up running ancient copies of it.
 install-exec-local:
-	rm -f ${bindir}/build-guile
+	echo "Hey, wouldn't it be funny if I were to do run this command right now:" ; \
+	echo "\"rm -f ${bindir}/build-guile\"?  Haha, that'd be insanely presumptuous."