Remove lzma as a specific build requirement

* bootstrap.conf: lzma was added as a build requirement
in the recently added build tools requirements check.
Remove that as it's quite new and also only required
for the make dist stage.

bootstrap.conf

@@ -171,7 +171,6 @@ gettext    -
 git        1.4.4
 gperf      -
 gzip       -
-lzma       -
 makeinfo   -
 perl       5.5
 rsync      -