talloc: fixes for sstate cache reuse

Fixes for sstate cache reuse between different build dirs. The
${SWIGLIBDIR##${STAGING_DIR_NATIVE}} had confused bitbake, bitbake would
add the "SWIGLIBDIR##${STAGING_DIR_NATIVE}" to the deps of do_install,
which caused the sstate cached can't be re-used.

Use another way for SWIGLIBDIR to fix the problem.

Signed-off-by: Robert Yang <liezhi.yang@windriver.com>
Signed-off-by: Wenzong Fan <wenzong.fan@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>