Thanks for your answer.
I did it but a bit differently.
On my dey-image-tiny, I added the beecrypt package to the IMAGE_INSTALL, then bitbake this image.
After flashing the target with this new image, I found under /usr/lib directory these two shared libraries:
libbeecrypt.so.7 & libbeecrypt.so.7.0.0 .
I took the libbeecrypt.so.7, renamed it to libbeecrypt.so and put it in the cross compile toolchain under:
It worked, because I have no more the error telling that the linker real-ld couldn't find -lbeecrypt .