fix build error without LDFLAGS

[sprhawk]

my custom recipe could be built under dunfell before. after I switch to hardknott, it reported: doesn't have GNU_HASH (didn't pass LDFLAGS?) [ldflags]

I added LDFLAGS into RUST_FLAGS

[posborne]

Hi @sprhawk, can you provide more information on the software you were building that required this along with the Yocto version and any other details? Sorry for missing this when it first came in.

[sprhawk]

@posborne hello, it was too long ago, I have forgotten it. I should be a c-interop library inside rust project, I was using hardknott

[posborne]

I believe other changes will resolve the root of this by fixing the linker wrapper script path.