gh-125269: Use `AC_LINK_IF_ELSE` to detect if `-latomic` is needed (#125416)

gh-125269: Use `AC_LINK_IF_ELSE` to detect if `-latomic` is needed (#125416)

We previously used `AC_RUN_IF_ELSE` with a short test program to detect
if `-latomic` is needed, but that requires choosing a specific default
value when cross-compiling because the test program is not run.
Some cross compilation targets like `wasm32-emscripten` do not support
`-latomic`, while other cross compilation targets, like
`arm-linux-gnueabi` require it.