gcc - Add dependency in libbacktrace -

i'm trying add dependency in makefile @ libbacktrace library.

however, seems i'm not using correct syntax it, i've tried:

depends+= +libbacktrace 

but receive following message -

package xxxx missing dependencies following libraries 

although libbacktrace included in -l (lib) path.

can offer solution?

thank in advance.

i've never seen plus sign in package name, want this:

depends += libbacktrace