workflows/test.yml: split building and running foo.exe

.github/workflows/test.yml

@@ -75,4 +75,17 @@ jobs:
               $flags += '-lpthread'
           }
           & '${{ steps.setup.outputs.clangxx }}' $flags
-          & (Join-Path . foo)
+
+      - name: Run foo.exe
+        run: |
+          $expected = @"
+          Doing something #1
+          Doing something #2
+          Doing something #3
+          "@
+          $actual = & (Join-Path . foo)
+          $actual = $actual -join [Environment]::NewLine
+          $($actual -eq $expected) -or $(throw @"
+          Unexpected output:
+          $actual
+          "@)