Fix missing lk_catalyst.so in LK editable installation (#945)

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------------------------------------------------------------------------------------------------------------

**Context:**

This PR is a fix for the
[issue](#939)
reported by @maliasadi.

[sc-76118]

**Description of the Change:**

**Benefits:**

**Possible Drawbacks:**

**Related GitHub Issues:**

---------

Co-authored-by: ringo-but-quantum <[email protected]>

.github/CHANGELOG.md

@@ -119,6 +119,9 @@
 
 ### Bug fixes
 
+* Fix missing `liblightning_kokkos_catalyst.so` in Lightning-Kokkos editable installation.
+  [(#945)](https://github.com/PennyLaneAI/pennylane-lightning/pull/945)
+
 * Add concept restriction to ensure `ConstMult` inline function only hit with arithmetic-values times complex values. Fixes build failures with the test suite when enabling OpenMP, and disabling BLAS and Python under clang.
   [(#936)](https://github.com/PennyLaneAI/pennylane-lightning/pull/936)
 

pennylane_lightning/core/_version.py

@@ -16,4 +16,4 @@
    Version number (major.minor.patch[-label])
 """
 
-__version__ = "0.39.0-dev44"
+__version__ = "0.39.0-dev45"

setup.py

@@ -156,6 +156,12 @@ def build_extension(self, ext: CMakeExtension):
             env=os.environ,
         )
 
+        # Ensure that catalyst shared object is copied to the build directory for pip editable install
+        if backend in ("lightning_kokkos"):
+            source = os.path.join(f"{extdir}", f"lib{backend}_catalyst.so")
+            destination = os.path.join(os.getcwd(), "build")
+            shutil.copy(source, destination)
+
 with open(os.path.join("pennylane_lightning", "core", "_version.py"), encoding="utf-8") as f:
     version = f.readlines()[-1].split()[-1].strip("\"'")