boottrap: fix paths embedded in .la files  - these are invalid for local setups since they have travis absolute paths by default  - this is not needed for building mapnik (since mapnik does not use libtool)  - but it enables using the result of mapnik-config to build apps that do use libtool  - so it unblocks building mod_tile against a local mapnik/mapnik-config built against mason
boottrap: fix paths embedded in .la files
 - these are invalid for local setups since they have travis absolute paths by default
 - this is not needed for building mapnik (since mapnik does not use libtool)
 - but it enables using the result of mapnik-config to build apps that do use libtool
 - so it unblocks building mod_tile against a local mapnik/mapnik-config built against mason

pnorman/mapnik,whuaegeanse/mapnik,CartoDB/mapnik,naturalatlas/mapnik,cjmayo/mapnik,pnorman/mapnik,tomhughes/mapnik,CartoDB/mapnik,mbrukman/mapnik,lightmare/mapnik,mapnik/mapnik,jwomeara/mapnik,naturalatlas/mapnik,zerebubuth/mapnik,mapnik/mapnik,pramsey/mapnik,pramsey/mapnik,stefanklug/mapnik,mapnik/mapnik,naturalatlas/mapnik,zerebubuth/mapnik,mapnik/mapnik,stefanklug/mapnik,lightmare/mapnik,cjmayo/mapnik,lightmare/mapnik,mbrukman/mapnik,pramsey/mapnik,jwomeara/mapnik,Uli1/mapnik,jwomeara/mapnik,mapycz/mapnik,pnorman/mapnik,Uli1/mapnik,stefanklug/mapnik,mapycz/mapnik,cjmayo/mapnik,tomhughes/mapnik,tomhughes/mapnik,stefanklug/mapnik,CartoDB/mapnik,mbrukman/mapnik,mbrukman/mapnik,mapycz/mapnik,Uli1/mapnik,pramsey/mapnik,cjmayo/mapnik,lightmare/mapnik,whuaegeanse/mapnik,zerebubuth/mapnik,tomhughes/mapnik,naturalatlas/mapnik,Uli1/mapnik,jwomeara/mapnik,pnorman/mapnik,whuaegeanse/mapnik,whuaegeanse/mapnik