thunderbird: Fix --with-thunderbird-plugin-dir configure argument
thunderbird: Fix --with-thunderbird-plugin-dir configure argument

The configure argument would not work and cause the configure script to abort
when used due to a typo.

outofbits/tracker,hoheinzollern/tracker,outofbits/tracker,hoheinzollern/tracker,hoheinzollern/tracker,outofbits/tracker,outofbits/tracker,outofbits/tracker,hoheinzollern/tracker,outofbits/tracker,hoheinzollern/tracker,hoheinzollern/tracker,outofbits/tracker,hoheinzollern/tracker