Test release flag in ci

Also, use the binaries built *with* the release flag as artifacts, so people can
download the fastest version available.

.gitlab-ci.yml

@@ -9,9 +9,16 @@ cache:
   paths:
     - .stack-root/
 
+
 test_branch:
   script:
-    - stack --no-terminal --system-ghc --no-install-ghc build --copy-bins --test --haddock --no-haddock-deps --bench --no-run-benchmarks --flag copar:benchmark-generators
+    - stack --no-terminal --system-ghc --no-install-ghc build --test --haddock --no-haddock-deps --bench --no-run-benchmarks --flag copar:benchmark-generators
+  except:
+    - master
+
+test_branch_release:
+  script:
+    - stack --no-terminal --system-ghc --no-install-ghc build --copy-bins --test --haddock --no-haddock-deps --bench --no-run-benchmarks --flag copar:benchmark-generators --flag copar:release
     - cp -r ~/.local/bin/ copar-linux-binaries
   except:
     - master
@@ -23,7 +30,14 @@ test_branch:
 
 test:
   script:
-    - stack --no-terminal --system-ghc --no-install-ghc build --copy-bins --test --haddock --no-haddock-deps --bench --no-run-benchmarks --flag copar:benchmark-generators
+    - stack --no-terminal --system-ghc --no-install-ghc build --test --haddock --no-haddock-deps --bench --no-run-benchmarks --flag copar:benchmark-generators
+  only:
+    - master
+
+
+test_release:
+  script:
+    - stack --no-terminal --system-ghc --no-install-ghc build --copy-bins --test --haddock --no-haddock-deps --bench --no-run-benchmarks --flag copar:benchmark-generators --flag copar:release
     - cp -r ~/.local/bin/ copar-linux-binaries
   only:
     - master