MAINT: add a release note

Author: ngoldbaum

doc/release/upcoming_changes/26750.improvement.rst

@@ -0,0 +1,12 @@
+`lapack_lite` is thread safe
+----------------------------
+
+NumPy provides a minimal CPU-only version of LAPACK named ``lapack_lite`` that can
+be used if no BLAS/LAPACK system is detected at build time.
+
+Until now, ``lapack_lite`` was not thread safe. Single-threaded use cases did
+not hit any issues, but running linear algebra operations in multiple threads
+could lead to errors, incorrect results, or seg faults due to data races.
+
+We have added a global lock, serializing access to ``lapack_lite`` in multiple
+threads.