only run system_time_conversions() test on 64bit systems.
it fails on 32bit systems with

---- time_store::test::system_time_conversions stdout ----
thread 'time_store::test::system_time_conversions' panicked at crates/tor-hsservice/src/time_store.rs:524:38:
2038-01-19T03:14:08Z: OutOfRange

diff --git a/crates/tor-hsservice/src/time_store.rs b/crates/tor-hsservice/src/time_store.rs
index 54be02664..ebe4cb904 100644
--- a/crates/tor-hsservice/src/time_store.rs
+++ b/crates/tor-hsservice/src/time_store.rs
@@ -518,6 +518,7 @@ mod test {
         assert_eq!(e, FutureTimestamp::from_str("T+23kg"));
     }
 
+    #[cfg(target_pointer_width = "64")]
     #[test]
     #[allow(clippy::unusual_byte_groupings)] // we want them to line up, dammit!
     fn system_time_conversions() {

--------------------------------------------------------------------------------
causes compile time overflows on pure 32bit builders

diff --git a/crates/tor-memquota/src/config.rs b/crates/tor-memquota/src/config.rs
index 0ed1241b1..05d33d2ce 100644
--- a/crates/tor-memquota/src/config.rs
+++ b/crates/tor-memquota/src/config.rs
@@ -457,6 +457,7 @@ mod test {
     }
 
     /// Test the logic that computes the `max` when configured as "auto".
+    #[cfg(target_pointer_width = "64")]
     #[test]
     // We do some `1 * X` operations below for readability.
     #[allow(clippy::identity_op)]
