CI: fix Windows build

This patch does three things:

1. Consolidates the build-main and build-pr configs into one.

2. Fixes the Windows build to actually do something, by adding
   the needed `shell: bash` lines into the .yml configuration.

3. Skips the deployment for all platforms except Linux, to
   avoid double deploys / failing releases.

.github/setup.sh

@@ -1,3 +1,10 @@
 #!/bin/sh
 curl -fsLO https://raw.githubusercontent.com/scijava/scijava-scripts/main/ci-setup-github-actions.sh
 sh ci-setup-github-actions.sh
+
+# Let the Linux build handle artifact deployment.
+if [ "$(uname)" != Linux ]
+then
+  echo "No deploy -- non-Linux build"
+  echo "NO_DEPLOY=1" >> $GITHUB_ENV
+fi

.github/workflows/build-main.yml → .github/workflows/build.yml

@@ -6,6 +6,9 @@ on:
       - master
     tags:
       - "*-[0-9]+.*"
+  pull_request:
+    branches:
+      - master
 
 jobs:
   build:
@@ -24,8 +27,10 @@ jobs:
           cache: 'maven'
       - name: Set up CI environment
         run: .github/setup.sh
+        shell: bash
       - name: Execute the build
         run: .github/build.sh
+        shell: bash
         env:
           GPG_KEY_NAME: ${{ secrets.GPG_KEY_NAME }}
           GPG_PASSPHRASE: ${{ secrets.GPG_PASSPHRASE }}