Fix CI?

Author: verhovsky

.appveyor.yml

@@ -1,5 +1,5 @@
 environment:
-  NODEJS_VERSION: "10"
+  NODEJS_VERSION: "14"
   PREBUILD_UPLOAD:
     secure: oNyyLE7/Oq3TUGZPz6DkLFPUuQzc8FiFS1iuPp7LZ2fyOP/UF4Np4NzJmWcXVyY/
 
@@ -10,7 +10,7 @@ platform:
 install:
   - ps: Install-Product node $env:NODEJS_VERSION $env:Platform
   - git submodule update --init --recursive
-  - npm install
+  - CXXFLAGS="--std=c++17" npm install
 
 build: off