ci(amd64/msvc): source vsdevcmd.bat

.drone.yml

@@ -15,7 +15,11 @@ steps:
 - name: unit tests
   shell: 'C:\Program Files\Microsoft Visual Studio\18\Enterprise\Common7\Tools\VsDevCmd.bat'
   commands: 
-    - ./tools/ci/amd64/msvc/unit_tests.ps1
+    - powershell.exe -NoProfile -Command "& {
+          Import-Module 'C:\Program Files\Microsoft Visual Studio\18\Enterprise\Common7\Tools\Microsoft.VisualStudio.DevShell.dll';
+          Enter-VsDevShell 1a3e2aa7 -SkipAutomaticLocation -DevCmdArguments '-arch=x64 -host_arch=x64';
+          ./tools/ci/amd64/msvc/unit_tests.ps1
+      }"
 
 ---
 kind: pipeline