ci: use fixed source path across runner steps

.gitea/workflows/build-windows-release.yml

@@ -31,8 +31,10 @@ jobs:
         run: |
           $ErrorActionPreference = 'Stop'
           $work = Join-Path $env:RUNNER_TEMP 'chengnan-src'
+          $srcFixed = Join-Path $env:RUNNER_TEMP 'chengnan-work'
           $zip = Join-Path $env:RUNNER_TEMP 'chengnan-src.zip'
           if (Test-Path $work) { Remove-Item -Recurse -Force $work }
+          if (Test-Path $srcFixed) { Remove-Item -Recurse -Force $srcFixed }
           if (Test-Path $zip) { Remove-Item -Force $zip }
           New-Item -ItemType Directory -Force -Path $work | Out-Null
 
@@ -44,8 +46,8 @@ jobs:
 
           $src = Get-ChildItem -Path $work -Directory | Select-Object -First 1
           if (-not $src) { throw 'Source archive extraction produced no directory' }
-          "SOURCE_DIR=$($src.FullName)" | Out-File -FilePath $env:GITHUB_ENV -Append -Encoding utf8
-          Write-Host "Source dir: $($src.FullName)"
+          Copy-Item -Path $src.FullName -Destination $srcFixed -Recurse -Force
+          Write-Host "Source dir: $srcFixed"
 
       - name: Install MSYS2 and build dependencies
         shell: powershell
@@ -73,7 +75,8 @@ jobs:
         run: |
           $ErrorActionPreference = 'Stop'
           $bash = "$env:MSYS2_ROOT\usr\bin\bash.exe"
-          $src = $env:SOURCE_DIR -replace '\\','/'
+          $srcWin = Join-Path $env:RUNNER_TEMP 'chengnan-work'
+          $src = $srcWin -replace '\\','/'
           $src = $src -replace '^([A-Za-z]):','/$1'
           $src = $src.ToLower()
           $script = @"