meson: add wrap for mapper

The phosphor-objmgr repository, which supplies libmapper, now
compiles using meson.  Add a wrap file for it to allow builds outside
of Yocto or an SDK.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Ic0c9fa2880a86116e03c5a26b51de4dd032baf4b
2 files changed