Unescape double quotes escaped by another double quote in defines

Otherwise, e.g. SRCDIR is defined as ""C:/lo/core"", which is not a
proper string literal.

Change-Id: Id7b503ea21735892b504dbc861f66c250db01e94
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/163902
Tested-by: Jenkins
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>

bin/gbuild-to-ide

@@ -1041,7 +1041,7 @@ class VisualStudioIntegrationGenerator(IdeIntegrationGenerator):
         for key, value in defs.items():
             define = key
             if value is not None:
-                define += '=' + VisualStudioIntegrationGenerator.escapepattern.sub(r'\1', value)
+                define += '=' + VisualStudioIntegrationGenerator.escapepattern.sub(r'\1', value).replace('""', '"')
             defines_list.append(define)
         return defines_list