fix: ci: restore stack.yaml as a regular file to fix CI

Github actions `hashFiles()` may not like symlinks, see comment in
push.yml.

.github/workflows/push.yml

@@ -100,6 +100,9 @@ jobs:
       uses: actions/cache@v2
       with:
         path: ~/.stack
+        # XXX if stack.yaml is a symlink, this fails with
+        #  Error: The template is not valid. .github/workflows/push.yml (Line: 103, Col: 14): hashFiles('**.yaml') failed. 
+        #  Fail to hash files under directory '/home/runner/work/hledger/hledger'
         key: ${{ runner.os }}-stack-global-${{ matrix.plan.ghc }}-${{ hashFiles('**.yaml') }}
         restore-keys: |
              ${{ runner.os }}-stack-global-${{ matrix.plan.ghc }}

stack.yaml

@@ -1 +0,0 @@
-stack9.0.yaml

stack.yaml

@@ -0,0 +1,39 @@
+# stack build plan using GHC 9.0.2
+
+nix:
+  pure: false
+  packages: [perl gmp ncurses zlib]
+
+resolver: nightly-2022-03-03
+
+# for https://gitlab.haskell.org/ghc/ghc/-/issues/20592 on mac m1 (adjust path if needed)
+extra-include-dirs:
+- /Library/Developer/CommandLineTools/SDKs/MacOSX12.1.sdk/usr/include/ffi
+
+packages:
+- hledger-lib
+- hledger
+- hledger-ui
+- hledger-web
+
+#extra-deps:
+# for hledger-lib:
+# for hledger:
+# for hledger-ui:
+# for hledger-web:
+# for Shake.hs:
+
+# for precise profiling, per https://www.tweag.io/posts/2020-01-30-haskell-profiling.html:
+# apply-ghc-options: everything
+# rebuild-ghc-options: true
+# stack build --profile --ghc-options="-fno-prof-auto"
+
+# tell GHC to write hie files, eg for weeder. Rumoured to be slow.
+# ghc-options:
+#   "$locals": -fwrite-ide-info
+
+# ghc-options:
+#   "$locals": -ddump-timings
+#  "$targets": -Werror
+#  "$everything": -O2
+#  some-package: -DSOME_CPP_FLAG