[llvm] Use MapVector to fix lld thinLTO bep issue. (PR #117551)

[via llvm-commits]

llvmssh wrote:

> What is "bep issue"?

Thanks for your reply. When a compiler of the same version builds the same project twice, the generated binary files are different, which is reflected in the inconsistent sequence in the symbol table.  For example:
< 295: 000000000000 0 FUNC  GLOBAL DEFAULT UND __lxstat at GLIBC_2.X 
>295: 000000000000  0 FUNC  GLOBAL DEFAULT UND __libc_start_main at GLIBC_2.X



https://github.com/llvm/llvm-project/pull/117551