[llvm] [RISCV] Adapt the element type of EVec into ContainerVT in lowerBUILD_VECTOR (PR #159373)

[Min-Yih Hsu via llvm-commits]

https://github.com/mshockwave commented:

(I actually checked the element type in a sibling patch #154847 but forgot to do that in #154450)
How does this compare to just not do the slideup optimization (i.e. fallback to the original slidedown lowering) upon mismatching element types?

https://github.com/llvm/llvm-project/pull/159373