Revert "Use common test build during CI (MetaMask#7196)" (MetaMask#7404)

This reverts commit b0ec610, which was
introduced in MetaMask#7196. This change was preventing the sourcemaps from
being uploaded correctly.

.circleci/config.yml

@@ -14,9 +14,6 @@ workflows:
       - prep-build:
           requires:
             - prep-deps
-      - prep-build-test:
-          requires:
-            - prep-deps
       # - prep-docs:
       #    requires:
       #      - prep-deps
@@ -28,10 +25,10 @@ workflows:
             - prep-deps
       - test-e2e-chrome:
           requires:
-            - prep-build-test
+            - prep-deps
       - test-e2e-firefox:
           requires:
-            - prep-build-test
+            - prep-deps
       - test-unit:
           requires:
             - prep-deps
@@ -129,24 +126,6 @@ jobs:
             - dist
             - builds
 
-  prep-build-test:
-    docker:
-      - image: circleci/node:10.16-browsers
-    steps:
-      - checkout
-      - attach_workspace:
-          at: .
-      - run:
-          name: Build extension for testing
-          command: yarn build:test
-      - run:
-          name: Move test build to 'dist-test' to avoid conflict with production build
-          command: mv ./dist ./dist-test
-      - persist_to_workspace:
-          root: .
-          paths:
-            - dist-test
-
   prep-docs:
     docker:
       - image: circleci/node:10.16-browsers
@@ -213,12 +192,9 @@ jobs:
       - checkout
       - attach_workspace:
           at: .
-      - run:
-          name: Move test build to dist
-          command: mv ./dist-test ./dist
       - run:
           name: test:e2e:chrome
-          command: yarn test:e2e:chrome
+          command: yarn build:test && yarn test:e2e:chrome
           no_output_timeout: 20m
       - store_artifacts:
           path: test-artifacts
@@ -234,12 +210,9 @@ jobs:
           command: ./.circleci/scripts/firefox-install
       - attach_workspace:
           at: .
-      - run:
-          name: Move test build to dist
-          command: mv ./dist-test ./dist
       - run:
           name: test:e2e:firefox
-          command: yarn test:e2e:firefox
+          command: yarn build:test && yarn test:e2e:firefox
           no_output_timeout: 20m
       - store_artifacts:
           path: test-artifacts