nodejs: Use provided python version

The build of nodejs uses python, and python leaking from the system can lead
to unexpected results, thus use provided from SlapOS.

/reviewed-on nexedi/slapos!319

component/nodejs/buildout.cfg

@@ -76,7 +76,7 @@ configure-options =
   --openssl-libpath=${openssl:location}/lib
 environment =
   HOME=${buildout:parts-directory}/${:_buildout_section_name_}
-  PATH=${pkgconfig:location}/bin:${patch:location}/bin:%(PATH)s
+  PATH=${pkgconfig:location}/bin:${patch:location}/bin:${python2.7:location}/bin:%(PATH)s
   PKG_CONFIG_PATH=${openssl:location}/lib/pkgconfig/
   CPPFLAGS=-I${zlib:location}/include
   LDFLAGS=-Wl,-rpath=${openssl:location}/lib -L${zlib:location}/lib -Wl,-rpath=${zlib:location}/lib