rust-bin.bbclass: look for RUNPATH instead of RPATH
rust-bin.bbclass: look for RUNPATH instead of RPATH

Poky 1.7 uses RPATH is now RUNPATH, so update our grep string appropriately.

Additionally, bitbake is having trouble with the automatic RDEPENDS on
rustlib.  Make it explicit for now.

starlab-io/meta-rust,cardoe/meta-rust,starlab-io/meta-rust,meta-rust/meta-rust,jmesmon/meta-rust,cardoe/meta-rust,meta-rust/meta-rust,meta-rust/meta-rust,cardoe/meta-rust,meta-rust/meta-rust,jmesmon/meta-rust,cardoe/meta-rust,meta-rust/meta-rust,jmesmon/meta-rust,jmesmon/meta-rust