build: correct alignment of "GEN version.i"

build: correct alignment of "GEN version.i"

Before:

    make[1]: Entering directory '/home/smarchi/build/babeltrace/src/common'
      CC       assert.lo
      CC       common.lo
      CC       uuid.lo
      CCLD     libbabeltrace2-common.la
      GEN        version.i

After:

    make[1]: Entering directory '/home/smarchi/build/babeltrace/src/common'
      CC       assert.lo
      CC       common.lo
      CC       uuid.lo
      CCLD     libbabeltrace2-common.la
      GEN      version.i

Change-Id: Ia4968e5209ef1afc83c287797f4d88756fe30b2f
Signed-off-by: Simon Marchi <simon.marchi@efficios.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/10094
Reviewed-by: Michael Jeanson <mjeanson@efficios.com>
Tested-by: jenkins <jenkins@lttng.org>