explicitly invoke cmd.exe

Author: kristjanvalur

.travis.yml

@@ -20,10 +20,10 @@ jobs:
       name: x64_msvc
       script:
         - cd vs2019
-        - ./build_x64.cmd && x64/Debug/test.exe
+        - cmd "/C build_x64.cmd" && x64/Debug/test.exe
     - os: windows
       name: x86_msvc
       script:
         - cd vs2019
-        - ./build_x86.cmd
+        - cmd "/C build_x86.cmd"
         - Win32/Debug/test.exe