perl: perlmod.mk: use flock when hostpkg/perl used

perl: perlmod.mk: use flock when hostpkg/perl used

Avoid parallel relinking and usage of the host perl binary by wrapping
its usage around flock calls.

Sometimes, two packages will try to relink the static host perl binary
at the same time.  Neither of them will have the other's module linked
in, and one of them will unavoidably clobber the other one's binary.

This will lead to errors when a package will not be able to find a
module that was supposed to be installed.

To fix that, an exclusive flock is used when relinking, with a 900
seconds timeout to avoid locking up the build process forever.

This is not enough because the binary may be concurrently used to build
another module package; perl is used in Configure, Compile, and Install
procedures.  If timing is right, a package will fail with a "permission
denied" error.

So a shared flock call is added in Configure, Compile, and Install
definitions for host and target, with a shorter, 300 seconds timeout.

Signed-off-by: Eneas U de Queiroz <cotequeiroz@gmail.com>