Replace the inline awk script with a Perl script which tracks the
dependencies recursively.
This allows to correctly track dependencies for files including files
with a second level include (for example: ffmpeg-devices.texi ->
devices.texi -> outdevs.texi).
This also adds a dependency on perl for computing the dependencies, which
should not be a problem since perl is already required all the way for
building documentation.
This is a variant of commit 628ceac652
which was reverted due to out-of-tree build failure.
Replace the inline awk script with a Perl script which tracks the
dependencies recursively.
This allows to correctly track dependencies for files including files
with a second level include (for example: ffmpeg-devices.texi ->
devices.texi -> outdevs.texi).
This also adds a dependency on perl for computing the dependencies, which
should not be a problem since perl is already required all the way for
building documentation.