Use webpack based string replacement

Doing the seddery in Makefile breaks `npm run build`, webpack watching,
and was generally brittle.

Revert the sed/make rules, and instead do the font replacement hacking
with `string-replace-loader`, which fits into webpack much more nicely.

There is still some potential simplification by not duplicating the
entire scss loader chain.

webpack.config.js

@@ -135,8 +135,45 @@ module.exports = {
                 use: babel_loader,
                 test: /\.(js|jsx)$/
             },
+            /* HACK: remove unwanted fonts from PatternFly's css */
+            {
+                test: /patternfly-4-cockpit.scss$/,
+                use: [
+                    extract.loader,
+                    {
+                        loader: 'css-loader',
+                        options: {
+                            sourceMap: true,
+                            url: false
+                        }
+                    },
+                    {
+                        loader: 'string-replace-loader',
+                        options: {
+                            multiple: [
+                                {
+                                    search: /src:url\("patternfly-icons-fake-path\/pficon[^}]*/g,
+                                    replace: "src:url('fonts/patternfly.woff')format('woff');",
+                                },
+                                {
+                                    search: /@font-face[^}]*patternfly-fonts-fake-path[^}]*}/g,
+                                    replace: '',
+                                },
+                            ]
+                        },
+                    },
+                    {
+                        loader: 'sass-loader',
+                        options: {
+                            sourceMap: true,
+                            outputStyle: 'compressed',
+                        },
+                    },
+                ]
+            },
             {
                 test: /\.s?css$/,
+                exclude: /patternfly-4-cockpit.scss/,
                 use: [
                     extract.loader,
                     {