Fix building from dist tarball with python bindings enabled

bindings/python/CMakeLists.txt

@@ -36,6 +36,7 @@ IF (BUILDING_FROM_VCS)
   )
 
   SET (SWIG_GNUCASH_CORE_C ${CMAKE_CURRENT_BINARY_DIR}/gnucash_core.c)
+  SET (SWIG_GNUCASH_CORE_C_PY ${CMAKE_CURRENT_BINARY_DIR}/gnucash_core_c.py)
 
   GNC_ADD_SWIG_PYTHON_COMMAND (swig-gnucash-core ${SWIG_GNUCASH_CORE_C}
     ${SWIG_FILES}
@@ -45,6 +46,7 @@ IF (BUILDING_FROM_VCS)
   )
 ELSE()
   SET (SWIG_GNUCASH_CORE_C gnucash_core.c)
+  SET (SWIG_GNUCASH_CORE_C_PY ${CMAKE_CURRENT_SOURCE_DIR}/gnucash_core_c.py)
 ENDIF()
 
 IF(WITH_PYTHON)
@@ -83,14 +85,14 @@ IF(WITH_PYTHON)
     LIBRARY DESTINATION ${PYTHON_SYSCONFIG_OUTPUT}/gnucash
     ARCHIVE DESTINATION ${PYTHON_SYSCONFIG_OUTPUT}/gnucash
   )
-  INSTALL(FILES ${PYEXEC_FILES} ${CMAKE_CURRENT_BINARY_DIR}/gnucash_core_c.py
+  INSTALL(FILES ${PYEXEC_FILES} ${SWIG_GNUCASH_CORE_C_PY}
     DESTINATION ${PYTHON_SYSCONFIG_OUTPUT}/gnucash
   )
 
   FILE(COPY ${PYEXEC_FILES} DESTINATION ${PYTHON_SYSCONFIG_BUILD}/gnucash)
 
   ADD_CUSTOM_TARGET(gnucash-core-c-py ALL
-    COMMAND ${CMAKE_COMMAND} -E copy ${CMAKE_CURRENT_BINARY_DIR}/gnucash_core_c.py ${PYTHON_SYSCONFIG_BUILD}/gnucash
+    COMMAND ${CMAKE_COMMAND} -E copy ${SWIG_GNUCASH_CORE_C_PY} ${PYTHON_SYSCONFIG_BUILD}/gnucash
     DEPENDS ${SWIG_GNUCASH_CORE_C})
 
   ADD_CUSTOM_TARGET(gnucash-core-c-build ALL