ci: Minor cleanup

* split into buildenv deps and stack build
* make the deps list more git-friendly
* use stack from github environment (I've seen the curl fail intermittently)
* indent consistency

.github/workflows/tests.yml

@@ -1,10 +1,10 @@
 name: Tests
 
 on:
-    pull_request:
-    push:
-        branches:
-        - master
+  pull_request:
+  push:
+    branches:
+      - master
 
 jobs:
   build:
@@ -36,11 +36,19 @@ jobs:
             ${{ runner.os }}-${{ matrix.resolver }}-${{ hashFiles(matrix.yaml) }}-
             ${{ runner.os }}-${{ matrix.resolver }}-
 
-      - name: Build and run tests
-        shell: bash
+      - name: Install dependencies
         run: |
-            set -ex
-            curl -sSL https://get.haskellstack.org/ | sh -s - -f
-            sudo apt install -y libasound2 libasound2-dev libxrandr-dev libtinfo-dev
-            sudo apt install -y libx11-dev libgmp-dev libxss-dev libxft-dev
-            stack --stack-yaml=${{ matrix.yaml }} test --fast --no-terminal --resolver=${{ matrix.resolver }}
+          set -ex
+          sudo apt install -y \
+            libasound2-dev \
+            libgmp-dev \
+            libtinfo-dev \
+            libx11-dev \
+            libxft-dev \
+            libxrandr-dev \
+            libxss-dev \
+            #
+      - name: Build and run tests
+        run: |
+          set -ex
+          stack --stack-yaml=${{ matrix.yaml }} test --fast --no-terminal --resolver=${{ matrix.resolver }}