.gitlab-ci.yml: Fix vcvars for powershell

.gitlab-ci.yml

@@ -118,7 +118,13 @@ build:linux:avx2:
   tags:
     - win32
   script:
-    - 'call "C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Auxiliary\Build\vcvarsall.bat" amd64'
+    - >
+      cmd.exe /c "call `"C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Auxiliary\Build\vcvars64.bat`" && set > %temp%\vcvars.txt"
+      Get-Content "$env:temp\vcvars.txt" | Foreach-Object {
+        if ($_ -match "^(.*?)=(.*)$") {
+          Set-Content "env:\$($matches[1])" $matches[2]
+        }
+      }
     - mkdir build
     - cd build
     - >