[compiler-rt] [compiler-rt] adding preadv2/pwritev2 interceptions. (PR #97216)

[Daniel Thornburgh via llvm-commits]

mysterymath wrote:

We're not running the test on Fuchsia, it's run on Fuchsia as part of the host build. Our glibc version is old enough that it doesn't include preadv2 or pwritev2. There needs to be a CMake compilation check that enables or disables the test.

https://github.com/llvm/llvm-project/pull/97216