package/kodi-*: run pkg-config at build time, not at parse time

When calling 'printvars' on a just-configured tree, the output contains
many spurious warnings about pkg-config being not found:

    make[1]: [...]/host/bin/pkg-config: Command not found

This is partly because a few packages call pkg-config at the time the
Makefile is parsed (really, right when make evaluates the recipe before
executing it).

It is customary, instead, to defer the call to pkg-config to the actual
shell running the recipe's commands, like all our other packages do.

Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Cc: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>