gitlab-ci: Use a stable path between build and test jobs on Windows

CTest expects the test suite to be executed from a build tree located
at its original path.  Set `GIT_CLONE_PATH` to use a fixed location.

.gitlab/ci/windows10.yml

@@ -1,3 +1,12 @@
+.windows_build:
+  variables:
+    # Note that shell runners only support runners with a single
+    # concurrency level. We can't use `$CI_CONCURRENCY_ID` because this may
+    # change between the build and test stages which CMake doesn't support.
+    # Even if we could, it could change if other runners on the machine
+    # could run at the same time, so we drop it.
+    GIT_CLONE_PATH: "$CI_BUILDS_DIR\\vtkm ci"
+
 .windows_vs2019:
   variables:
     VCVARSALL: "${VS160COMNTOOLS}\\..\\..\\VC\\Auxiliary\\Build\\vcvarsall.bat"
@@ -6,6 +15,7 @@
 
 .cmake_build_windows: &cmake_build_windows
   extends:
+    - .windows_build
     - .windows_vs2019
   stage: build
   timeout:  2 hours
@@ -47,6 +57,7 @@
 
 .cmake_test_windows: &cmake_test_windows
   extends:
+    - .windows_build
     - .windows_vs2019
   stage: test
   timeout:  50 minutes
@@ -65,7 +76,7 @@
 build:windows_vs2019:
   tags:
     - vtkm # Since this is a bare runner, pin to a project.
-    - concurrent
+    - nonconcurrent
     - build
     - windows
     - shell
@@ -85,7 +96,7 @@ build:windows_vs2019:
 test:windows_vs2019:
   tags:
     - vtkm # Since this is a bare runner, pin to a project.
-    - concurrent
+    - nonconcurrent
     - test
     - windows
     - shell