build: gen-version-i.sh: use `mv -f`

build: gen-version-i.sh: use `mv -f`

When file src/common/version.i happens to be owned by root (there are
known bugs that causes version.i to be rebuilt when doing `make install`
as root), doing `make` as a regular user gives an interactive prompt:

    make[3]: Entering directory '/home/smarchi/build/babeltrace/src/common'
      GEN      version.i
    mv: replace 'version.i', overriding mode 0644 (rw-r--r--)?

Pass -f to mv to avoid this.

Change-Id: I3ac19cff615fd52db1c025b08c046d34814fb50a
Signed-off-by: Simon Marchi <simon.marchi@efficios.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/10102
Reviewed-by: Michael Jeanson <mjeanson@efficios.com>