shellinabox: fix environment. version up to v2.18.

component/shellinabox/buildout.cfg

 [buildout]
 extends =
-  ../zlib/buildout.cfg
-  ../openssl/buildout.cfg
-  ../patch/buildout.cfg
-  ../automake/buildout.cfg
   ../autoconf/buildout.cfg
-  ../libtool/buildout.cfg
+  ../automake/buildout.cfg
   ../git/buildout.cfg
+  ../libtool/buildout.cfg
+  ../m4/buildout.cfg
+  ../openssl/buildout.cfg
+  ../patch/buildout.cfg
+  ../zlib/buildout.cfg
 
 parts = shellinabox
 
@@ -35,7 +36,7 @@ patches =
 ; This version has much more features, but does not support IPv6 (support unix domain though)
 recipe = slapos.recipe.build:gitclone
 repository = https://github.com/shellinabox/shellinabox
-revision = 458cd7aa8f513f41f7eee389fa5ff6a51acea593
+revision = b8285748993c4c99e80793775f3d2a0a4e962d5a
 git-executable = ${git:location}/bin/git
 
 [shellinabox-github]
@@ -45,5 +46,5 @@ configure-command =
   ${libtool:location}/bin/libtoolize
   ${autoconf:location}/bin/autoreconf -vif
   ./configure
-environment =
-  PATH=${autoconf:location}/bin:${automake:location}/bin:${libtool:location}/bin:%(PATH)s
+environment +=
+  PATH=${autoconf:location}/bin:${automake:location}/bin:${libtool:location}/bin:${m4:location}/bin:%(PATH)s