When Windows build is executed, cscript is used to execute JavaScript files.
This uses cscript from the system to execute *.js files. cscript is not
only capable of executing JavaScript, but also VBScript. Which engine to
run is usually determined by the file extension, except when any installed
program has added a registered association to the used file type. In that
case, the execution of cscript and thus the build fails. This can be prevented
by directly defining the script engine when calling cscript, using the
/e:javascript parameter for *.js targets.

Change-Id: If717b8ae5335acbe4f11c269d3c98a7247a135e6
Reviewed-on: https://gerrit.libreoffice.org/21717Reviewed-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>
Tested-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>