rust: tests: add Kconfig for KUnit test

There are 6 individual Rust KUnit test suites (plus the doctests one). All
the tests are compiled unconditionally now, which adds ~200 kB to the
kernel image for me on x86_64. As Rust matures, this bloating will
inevitably grow.

Add Kconfig.test which includes a RUST_KUNIT_TESTS menu, and all
individual tests under it.

As usual, new tests are all enabled if KUNIT_ALL_TESTS=y.

Suggested-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Yury Norov <ynorov@nvidia.com>
Reviewed-by: David Gow <david@davidgow.net>
Acked-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260417031531.315281-3-ynorov@nvidia.com
[ Fixed capitalization. Used singular for "API" for consistency.
  Reworded to clarify these are suites and that there exists
  the doctests one (which is the biggest at the moment by
  far). - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/rust/kernel/str.rs b/rust/kernel/str.rs
index 8311d91549e1..a435674f05ea 100644
--- a/rust/kernel/str.rs
+++ b/rust/kernel/str.rs
@@ -415,6 +415,7 @@ macro_rules! c_str {
     }};
 }
 
+#[cfg(CONFIG_RUST_STR_KUNIT_TEST)]
 #[kunit_tests(rust_kernel_str)]
 mod tests {
     use super::*;