[libc][bazel] Allow configure options to alter all targets (#89251)

The previous state was leading to inconsistencies. Some targets would
get the options and some wouldn't. As an example, the `MEMORY_COPTS`
definitions would only apply to the `:string_memory_utils` target but
not to the `:memcpy` target. This patch makes sure definitions are
applied throughout the LLVM libc targets as `local_defines`. This
ensures that the preprocessor definitions don't propagate to depending
targets outside of LLVM libc, and that all libc targets have consistent
preprocessor definitions.