Bug#649713: Please Build-Depend on ghostscript, not gs-common.
flite currently Build-Depends on gs-common, which is a transitional package.
The next upload of ghostscript (currently) plans to drop both gs-common and
the ghostscript "Provides: gs-common". As soon as that upload happens, it
will make flite FTBFS.
Please replace the Build-Depends on gs-common to a Build-Depends on ghostscript.
(The severity of this bug will be raised after the ghostscript upload.)