[compiler-rt] Fix interceptors with Solaris as (#72973)

Jakub Jelínek reports:

As mentioned in https://gcc.gnu.org/PR112563, the new DECLARE_WRAPPER
macro
added in 37445e96 and ammended in 85d3873a

 doesn't work on SPARC/Solaris
with
  Solaris as.

While clang and GNU as when used from GCC seems to be forgiving on most
architectures and allow both %function and @function (with the latter
not being
allowed on ARM/AArch64 I believe because @ is assembler comment start
there),
  Solaris as doesn't allow the %function form.

Fix it by using %function only for ARM.

Co-developed-by: Jakub Jelínek <jakub@redhat.com>
Reported-by: Jakub Jelínek <jakub@redhat.com>
Closes: https://github.com/llvm/llvm-project/issues/72970