build: remove cctest extension

cctest has `so.59` extension when building node shared library in linux.
The appending is defined in node.gypi and the cctest target in node.gyp
includes node.gypi. Moving the appending from node.gypi to node target
in node.gyp fixes the issue.

Signed-off-by: Yihong Wang <yh.wang@ibm.com>

PR-URL: nodejs#16680
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>

node.gypi

@@ -11,11 +11,6 @@
       'defines': [
         'NODE_SHARED_MODE',
       ],
-      'conditions': [
-        [ 'node_module_version!="" and OS!="win"', {
-          'product_extension': '<(shlib_suffix)',
-        }]
-      ],
     }],
     [ 'node_enable_d8=="true"', {
       'dependencies': [ 'deps/v8/src/d8.gyp:d8' ],