azure: Enable vs2015 jobs

Don't run MPI runtime installer, which fails with vs2015 image

azure-pipelines.yml

@@ -10,24 +10,24 @@ variables:
   CI: 1
 
 jobs:
-#- job: vs2015
-#  pool:
-#    vmImage: vs2015-win2012r2
-#
-#  strategy:
-#    maxParallel: 10
-#    matrix:
-#        vc2015x86ninja:
-#          arch: x86
-#          compiler: msvc2015
-#          backend: ninja
-#        vc2015x86vs:
-#          arch: x86
-#          compiler: msvc2015
-#          backend: vs2015
-#
-#  steps:
-#  - template: ci/azure-steps.yml
+- job: vs2015
+  pool:
+    vmImage: vs2015-win2012r2
+
+  strategy:
+    maxParallel: 10
+    matrix:
+        vc2015x86ninja:
+          arch: x86
+          compiler: msvc2015
+          backend: ninja
+        vc2015x86vs:
+          arch: x86
+          compiler: msvc2015
+          backend: vs2015
+
+  steps:
+  - template: ci/azure-steps.yml
 
 - job: vs2017
   pool:

ci/azure-steps.yml

@@ -31,8 +31,11 @@ steps:
      DownloadFile -Source 'http://nirbheek.in/files/binaries/pkg-config/win32/pkg-config.exe' -Destination $(System.WorkFolder)\pkg-config.exe
      DownloadFile -Source 'https://download.microsoft.com/download/D/B/B/DBB64BA1-7B51-43DB-8BF1-D1FB45EACF7A/msmpisdk.msi' -Destination msmpisdk.msi
      DownloadFile -Source 'https://download.microsoft.com/download/D/B/B/DBB64BA1-7B51-43DB-8BF1-D1FB45EACF7A/MSMpiSetup.exe' -Destination MSMpiSetup.exe
-     Start-Process msiexec.exe -ArgumentList '/i msmpisdk.msi /quiet' -Wait
-     Start-Process .\MSMpiSetup.exe -ArgumentList '-unattend -full' -Wait
+     if ($env:compiler -ne 'msvc2015') {
+       Start-Process msiexec.exe -ArgumentList '/i msmpisdk.msi /quiet' -Wait
+       # installer fails "requires an interactive window station" with vs2015 image
+       Start-Process .\MSMpiSetup.exe -ArgumentList '-unattend -full' -Wait
+     }
 
      # import ms-mpi env vars (set by installer)
      foreach ($p in "MSMPI_INC", "MSMPI_LIB32", "MSMPI_LIB64") {