doc: fix documentation about how to enable C++ exception (#1059)

* doc: fixed doc about how to enable C++ exceptions.

PR-URL: #1059
Reviewed-By: Michael Dawson <[email protected]>

Author: NickNaso

doc/setup.md

@@ -39,14 +39,25 @@ To use **Node-API** in a native module:
 ```gyp
   'cflags!': [ '-fno-exceptions' ],
   'cflags_cc!': [ '-fno-exceptions' ],
-  'xcode_settings': {
-    'GCC_ENABLE_CPP_EXCEPTIONS': 'YES',
-    'CLANG_CXX_LIBRARY': 'libc++',
-    'MACOSX_DEPLOYMENT_TARGET': '10.7',
-  },
-  'msvs_settings': {
-    'VCCLCompilerTool': { 'ExceptionHandling': 1 },
-  },
+  'conditions': [
+    ["OS=='win'", {
+      "defines": [
+        "_HAS_EXCEPTIONS=1"
+      ],
+      "msvs_settings": {
+        "VCCLCompilerTool": {
+          "ExceptionHandling": 1
+        },
+      },
+    }],
+    ["OS=='mac'", {
+      'xcode_settings': {
+        'GCC_ENABLE_CPP_EXCEPTIONS': 'YES',
+        'CLANG_CXX_LIBRARY': 'libc++',
+        'MACOSX_DEPLOYMENT_TARGET': '10.7',
+      },
+    }],
+  ],
 ```
 
   Alternatively, disable use of C++ exceptions in Node-API: