[llvm] [RISCV] Add areInlineCompatible for riscv target (PR #86639)

[Jianjian Guan via llvm-commits]

jacquesguan wrote:

> Does this mean we'll inline a function even if it we disabled an extension via an overriding target attribute arch string? e.g.
> 
> ```c
> __attribute__((target("arch=rv64i")))
> float foo(float x) {
>   return x + 42;
> }
> 
> float bar(float x) {
>   return foo(x);
> }
> ```
> 
> foo will now be inlined if we compile with `-march=rv64if`. But I presume that's fine given that this seems to be inline with what other targets do

Yes, in my work, there are some similar cases. I have some common tool functions and want to inline them into some users with 
 different target attributes. 

https://github.com/llvm/llvm-project/pull/86639