freetype: drop calling autogen, no longer needed

freetype: drop calling autogen, no longer needed

In commit a31a66802a7a1af76a629b0ba7120424ed547646 ("freetype:
security bump to version 2.5.3"), the freetype package was changed to
call ./autogen.sh to regenerate the autotools stuff, because the
ltmain.sh provided by upstream freetype was not compatible with
Buildroot libtool-patching logic.

Since then, freetype has been bumped several times, and the current
version packaged in Buildroot has an ltmain.sh that is compatible with
our libtool-patching logic.

Therefore, this commit drops the no longer needed autogen stuff.

This autogen stuff was badly breaking per-package host/target
directory, because the autogen happened at the post-patch hook step,
at which point the host-automake/host-autoconf/host-libtool
dependencies have not yet been copied into this package host
directory.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>