Build depedency fix - build backend libararies before the guile bindings

Compiling our guile scripts will run loaded libraries. One of the libraries to
load is the engine library which expects to find the enabled backends (xml and or dbi).
If those aren't built yet, this will result in error messages printed in the build output.

bindings/guile/CMakeLists.txt

@@ -70,7 +70,14 @@ install(TARGETS gnucash-guile
 set (core_utils_SCHEME core-utils.scm)
 
 set(GUILE_OUTPUT_DIR   gnucash)
-set(GUILE_DEPENDS      gnc-core-utils gnucash-guile)
+set(GUILE_DEPENDS
+    gnc-core-utils
+    gnucash-guile
+    gncmod-backend-xml)
+
+if(WITH_SQL)
+    list(APPEND GUILE_DEPENDS gncmod-backend-dbi)
+endif()
 
 gnc_add_scheme_targets(scm-core-utils
     SOURCES "${core_utils_SCHEME}"