double arrow icons in b-form-select if scss is imported

Describe the bug

A clear and concise description of what the bug is.

Steps to reproduce the bug

1. git clone [e-mail]:kzw/vuetest.git
2. npm i && npm run dev
3. See double arrows in form select
4. In css and override branches you will not see double arrows

Expected behavior

A clear and concise description of what you expected to happen.

Versions

Libraries:

• BootstrapVue: 2.3.0
• Bootstrap: 4.4.1
• Vue: 2.6.11

Environment:

• Device: mac
• OS: 10.15
• Browser: chrome, ff, safari
• Version: latest

Demo link

Additional context

In branch css I use https://bootstrap-vue.org/docs/#vue-cli-3 to import css files into main.js

In branch override I use a style as recommended in https://stackoverflow.com/questions/48287610/bootstrap-4-beta-options-menu-has-double-dropdown-icons/48288103

In branch master I use instructions in https://bootstrap-vue.org/docs/#using-module-bundlers to import custom.scss into main.js

I had also been creating custom.css from custom.scss using sass command line utility and then importing custom.css with the same double arrow bug. This approach is not in any branches though.

I believe that there is something wrong with merging bootstrap and bootstrap-vue in scss first.

[tmorehouse]

And when compiling the SCSS we do:

node-sass --output-style expanded \
          --source-map true \
          --source-map-contents true \
          --precision 6 \
          scripts/build.scss \
          dist/bootstrap-vue.css
postcss --config scripts/postcss.config.js \
        --replace dist/bootstrap-vue.css

To auto prefix based on our browserlist.rc file

[tmorehouse]

When auto-prefixer is used when compiling the SCSS, you should see:

If you only see appearance: none and not the prefixed versions as well, then you are missing auto-prefixer in your SASS postcss compile pipeline.

In our postcss.config.js we have:

module.exports = ctx => ({
  map: {
    inline: false,
    annotation: true,
    sourcesContent: true
  },
  plugins: {
    autoprefixer: {
      cascade: false
    }
  }
})