CI: improve the build script

1. Try to fix the Windows build, as described at
   <https://stackoverflow.com/a/75758843/1207769>.
   But reports there are inconsistent about whether it works.

2. Combine the output files into a single artifact.
   Each artifact gets zipped anyway, so may as well group them.
   Still more to do in this regard: add jaunch.toml to the artifact,
   and name the configurator binaries with an os-arch suffix, so that
   multiple configurators can coexist in the same portable application.

3. Make a couple of minor cosmetic tweaks to the YAML.

.github/workflows/build.yml

@@ -2,11 +2,9 @@ name: build
 
 on:
   push:
-    branches:
-      - main
+    branches: [main]
   pull_request:
-    branches:
-      - main
+    branches: [main]
 
 jobs:
   build:
@@ -17,6 +15,10 @@ jobs:
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
 
+    defaults:
+      run:
+        shell: bash
+
     steps:
     - uses: actions/checkout@v4
 
@@ -32,9 +34,6 @@ jobs:
     - uses: actions/upload-artifact@v4
       with:
         name: launcher-${{ matrix.os }}
-        path: build/launcher*
-
-    - uses: actions/upload-artifact@v4
-      with:
-        name: jaunch-${{ matrix.os }}
-        path: build/bin/*/releaseExecutable/jaunch.k?exe
+        path: |
+          build/launcher*
+          build/bin