component/slapos: Take BUILD_DIRECTORY from buildout section

component/slapos/obs.cfg

@@ -2,6 +2,7 @@
 # You need to define rootdir and destdir on an upper level
 #rootdir = %TARGET_DIRECTORY%
 #destdir = %BUILD_ROOT_DIRECTORY% 
+#builddir = %BUILD_DIRECTORY%
 extends =
   buildout.cfg
 
@@ -32,7 +33,7 @@ environment +=
 environment =
   PATH=${perl:location}/bin:${lunzip:location}/bin:%(PATH)s
   CPPFLAGS=-I${libxml2:location}/include -I${zlib:location}/include -I${ncurses:location}/include
-  LDFLAGS=-L${libxml2:location}/lib -Wl,-rpath=${libxml2:location}/lib -L${zlib:location}/lib -Wl,-rpath=${zlib:location}/lib -L${ncurses:location}/lib -Wl,-rpath=${ncurses:location}/lib -Wl,-rpath=%BUILD_DIRECTORY%/parts/${:_buildout_section_name_}/lib
+  LDFLAGS=-L${libxml2:location}/lib -Wl,-rpath=${libxml2:location}/lib -L${zlib:location}/lib -Wl,-rpath=${zlib:location}/lib -L${ncurses:location}/lib -Wl,-rpath=${ncurses:location}/lib -Wl,-rpath=${buildout:builddir}/parts/${:_buildout_section_name_}/lib
 
 [bison]
 configure-options +=