build: enable cctest to use generated objects

This commit tries to make it simpler to add unit tests (cctest) for
code that needs to test node core funtionality but that might not be
appropriate as an addon or a JavaScript test. An example of this could
be adding functionality targeted for situations when Node itself is
embedded.

Currently it was not as easy, or efficient, as one would have hoped to
add such tests. The object output directories vary for different
operating systems which we need to link to so that we don't have an
additional compilation step.

PR-URL: #11956
Backport-PR-URL: #12948
Ref: #9163
Reviewed-By: James M Snell <jasnell@gmail.com>

common.gypi

@@ -35,16 +35,25 @@
       ['OS == "win"', {
         'os_posix': 0,
         'v8_postmortem_support%': 'false',
+        'OBJ_DIR': '<(PRODUCT_DIR)/obj',
+        'V8_BASE': '<(PRODUCT_DIR)/lib/v8_libbase.lib',
       }, {
         'os_posix': 1,
         'v8_postmortem_support%': 'true',
       }],
-      ['GENERATOR == "ninja" or OS== "mac"', {
-        'OBJ_DIR': '<(PRODUCT_DIR)/obj',
+      ['OS== "mac"', {
+        'OBJ_DIR': '<(PRODUCT_DIR)/obj.target',
         'V8_BASE': '<(PRODUCT_DIR)/libv8_base.a',
       }, {
-        'OBJ_DIR': '<(PRODUCT_DIR)/obj.target',
-        'V8_BASE': '<(PRODUCT_DIR)/obj.target/deps/v8/tools/gyp/libv8_base.a',
+        'conditions': [
+          ['GENERATOR=="ninja"', {
+            'OBJ_DIR': '<(PRODUCT_DIR)/obj',
+            'V8_BASE': '<(PRODUCT_DIR)/obj/deps/v8/tools/gyp/libv8_base.a',
+          }, {
+            'OBJ_DIR%': '<(PRODUCT_DIR)/obj.target',
+            'V8_BASE%': '<(PRODUCT_DIR)/obj.target/deps/v8/tools/gyp/libv8_base.a',
+          }],
+        ],
       }],
       ['openssl_fips != ""', {
         'OPENSSL_PRODUCT': 'libcrypto.a',