Fix test-import-backend failure.

Linking gnc-engine caused an ODR violation in gnc-date.cpp. Instead
fake qof_log_check() in gtest-import-backend.cpp.

gnucash/import-export/test/CMakeLists.txt

@@ -48,7 +48,6 @@ set(gtest_import_backend_INCLUDE_DIRS
 )
 
 set(gtest_import_backend_LIBS
-  gnc-engine
   PkgConfig::GTK3
   ${Boost_LIBRARIES}
   ${GMODULE_LDFLAGS}

gnucash/import-export/test/gtest-import-backend.cpp

@@ -61,6 +61,13 @@ qof_log_prettify (const char *name)
     return name;
 }
 
+// Fake qof_log_check suppresses logging.
+gboolean
+qof_log_check(QofLogModule log_module, QofLogLevel log_level)
+{
+    return FALSE;
+}
+
 // fake function from engine-helpers.c
 // this is a slightly modified version of the original function
 const char *