component/openblas: use default SlapOS gcc.

otherwise we can have "gfortran: not found" error.

component/openblas/buildout.cfg

 [buildout]
 extends =
+  ../gcc/buildout.cfg
   ../perl/buildout.cfg
 
 parts =
@@ -31,4 +32,4 @@ make-options =
 make-targets =
   PREFIX="@@LOCATION@@" install
 environment =
-  PATH=${perl:location}/bin:%(PATH)s
+  PATH=${gcc:prefix}/bin:${perl:location}/bin:%(PATH)s