added implicit make rule for .gdb suffix to set XBSV_DEBUG=1, e.g. echo.zedrun.gdb
added implicit make rule for .gdb suffix to set XBSV_DEBUG=1, e.g. echo.zedrun.gdb

Change-Id: Iefbc3be69df6a96626e3c372d1bd12debb8cdf07

csail-csg/connectal,cambridgehackers/connectal,hanw/connectal,hanw/connectal,8l/connectal,csail-csg/connectal,hanw/connectal,chenm001/connectal,cambridgehackers/connectal,8l/connectal,chenm001/connectal,8l/connectal,chenm001/connectal,cambridgehackers/connectal,hanw/connectal,chenm001/connectal,8l/connectal,csail-csg/connectal,hanw/connectal,cambridgehackers/connectal,csail-csg/connectal,8l/connectal,chenm001/connectal,cambridgehackers/connectal,csail-csg/connectal