[WIP][CI] Build Windows packages within virtualenv (#709)

* try venv for win64

* update

* update

* trying another

* update

* update

* update

* trigger ci

* update

* update

Jenkinsfile

@@ -293,4 +293,11 @@ pipeline {
       }
     }
   }
+  post {
+    always {
+      node('windows') {
+        bat "rmvirtualenv ${BUILD_TAG}"
+      }
+    }
+  }
 }

tests/scripts/build_dgl.bat

 @ECHO OFF
 SETLOCAL EnableDelayedExpansion
 
+CALL mkvirtualenv --system-site-packages %BUILD_TAG%
 DEL /S /Q build
 DEL /S /Q _download
 MD build
@@ -15,7 +16,7 @@ POPD
 
 PUSHD python
 DEL /S /Q build *.egg-info dist
-pip install -e . --force-reinstall --user || EXIT /B 1
+pip install -e . || EXIT /B 1
 POPD
 
 ENDLOCAL

tests/scripts/task_example_test.bat

@@ -15,6 +15,7 @@ IF x%1x==xx (
 	ECHO Must supply CPU or GPU
 	GOTO :FAIL
 )
+CALL workon %BUILD_TAG%
 
 SET DGLBACKEND=pytorch
 SET DGL_LIBRARY_PATH=!CD!\build

tests/scripts/task_unit_test.bat

@@ -7,6 +7,7 @@ IF x%1x==xx (
 ) ELSE (
 	SET BACKEND=%1
 )
+CALL workon %BUILD_TAG%
 
 SET PYTHONPATH=tests;!CD!\python;!PYTHONPATH!
 SET DGLBACKEND=!BACKEND!