package/pkg-luarocks: drop flock at installation time

package/pkg-luarocks: drop flock at installation time

In commit 22b327fc743b48a33aec0a9190bd67118641b294 ("pkg-luarocks: fix
top-level parallel makefile support"), a flock on $(TARGET_DIR) was
added to ensure that two Luarocks packages are not installed at the
same time.

However, to support top-level parallel build, we have now clearly
decided that per-package folders is a requirement. Therefore,
TARGET_DIR is anyway going to be different for each package, making
this flock unnecessary.

Trying to use top-level parallel build without per-package folder is
simply not supported, so this commit drops the unnecessary flock.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Acked-by: Francois Perrad <francois.perrad@gadz.org>