AppVeyor: Use & instead of && (see #278)

appveyor.yml

@@ -107,8 +107,8 @@ install:
   - if not exist C:\ssl\ (md C:\ssl\)
   - if not exist C:\ssl\Win32OpenSSL_102h.exe (curl http://slproweb.com/download/Win32OpenSSL-1_0_2g.exe -o C:\ssl\Win32OpenSSL_102h.exe)
   - if not exist C:\ssl\Win64OpenSSL_102h.exe (curl http://slproweb.com/download/Win64OpenSSL-1_0_2g.exe -o C:\ssl\Win64OpenSSL_102h.exe)
-  - C:\ssl\Win32OpenSSL_102h.exe /SILENT /LOG="C:\ssl\install_ssl32.log" && exit 0
-  - C:\ssl\Win64OpenSSL_102h.exe /SILENT /LOG="C:\ssl\install_ssl64.log" && exit 0
+  - C:\ssl\Win32OpenSSL_102h.exe /SILENT /LOG="C:\ssl\install_ssl32.log" & exit 0
+  - C:\ssl\Win64OpenSSL_102h.exe /SILENT /LOG="C:\ssl\install_ssl64.log" & exit 0
   - dir C:\ssl