Take a different approach to making the flags match...

`stack path --fast ...` says "Invalid option `--fast'"

.circleci/config.yml

@@ -110,7 +110,6 @@ jobs:
             BUILD="stack build \
             --no-terminal \
             --only-dependencies \
-            --fast \
             --jobs 1 \
             --interleaved-output"
             nix-shell shell.nix --run "$BUILD"
@@ -140,17 +139,11 @@ jobs:
             # --no-terminal avoids having fancy progress reports written to
             # stdout.
             #
-            # --fast turns off compiler optimizations which probably doesn't
-            # make a lot of difference in our code but it can speed up build
-            # times for our dependencies (as well as reduce compiler memory
-            # usage which may be important at least for stripe-core).
-            #
             # --haddock builds the Haskell API documentation.
             # --haddock-internal builds docs even for unexposed modules.
             # --no-haddock-deps skips building docs for all our dependencies.
             BUILD="stack build \
               --no-terminal \
-              --fast \
               --haddock \
               --haddock-internal \
               --no-haddock-deps"
@@ -169,7 +162,7 @@ jobs:
       - run:
           name: "Prepare Artifacts for Upload"
           command: |
-            mv $(nix-shell shell.nix --run "stack path --fast --local-doc-root")/PaymentServer-* /tmp/PaymentServer-docs
+            mv $(nix-shell shell.nix --run "stack path --local-doc-root")/PaymentServer-* /tmp/PaymentServer-docs
 
       - store_artifacts:
           # This contains the html haddock output for the project.