[llvm] [JITLink][AArch32] Add explicit visibility macros to functions needed by unittests (PR #116557)

[Saleem Abdulrasool via llvm-commits]

compnerd wrote:

The declaration and definition must match (that is an error). So the declaration must be `__declspec(dllexport)` if there is a definition. You cannot have a declaration that is `__declspec(dllimport)` and then a definition.

That said, if you incorrectly mark the symbol as dllimport and then define it elsewhere within the module, that is generally a linker warning (but it will try to create a thunk to workaround it).

https://github.com/llvm/llvm-project/pull/116557