fix: failure when build directory contains spaces

Fix an installation issue that occurs when a path in which node-gyp is
run contains spaces.

For a path like `my app`, it would error with this message:

```
clang: error: no such file or directory: 'app/node_modules/node-addon-api'
```

The "my" part before the space (and the rest of the path before it)
would be missing from the path in the error message.

Fixes nodejs/node-gyp#65

pylib/gyp/generator/make.py

@@ -1418,7 +1418,12 @@ def WriteSources(
             includes = config.get("include_dirs")
             if includes:
                 includes = [Sourceify(self.Absolutify(i)) for i in includes]
-            self.WriteList(includes, "INCS_%s" % configname, prefix="-I")
+            self.WriteList(
+                includes,
+                "INCS_%s" % configname,
+                prefix="-I",
+                quoter=EscapeShellArgument
+            )
 
         compilable = list(filter(Compilable, sources))
         objs = [self.Objectify(self.Absolutify(Target(c))) for c in compilable]