ci: fix Windows tests silently passing on failure (#2294)

PowerShell doesn't stop on non-zero exit codes by default. `go test`
failures were ignored, and the step reported success because the
subsequent caddy tests passed.

Caught on this job, which fails but is green:
https://github.com/php/frankenphp/actions/runs/23424633971/job/68136742625?pr=2287

.github/workflows/windows.yaml

@@ -229,6 +229,8 @@ jobs:
           $env:PHPRC = Get-Location
 
           go test -race ./...
+          if ($LASTEXITCODE -ne 0) { exit $LASTEXITCODE }
           cd caddy
           go test -race ./...
+          if ($LASTEXITCODE -ne 0) { exit $LASTEXITCODE }
         working-directory: ${{ github.workspace }}\frankenphp

frankenphp_test.go

@@ -23,6 +23,7 @@ import (
 	"os"
 	"os/exec"
 	"os/user"
+	"runtime"
 	"path/filepath"
 	"strconv"
 	"strings"
@@ -1315,6 +1316,10 @@ func testOpcachePreload(t *testing.T, opts *testOptions) {
 		t.Skip("This test is only supported in PHP 8.3 and above")
 		return
 	}
+	if runtime.GOOS == "windows" {
+		t.Skip("opcache.preload is not supported on Windows")
+		return
+	}
 
 	cwd, _ := os.Getwd()
 	preloadScript := cwd + "/testdata/preload.php"