Force scheme to make links before any builds.

The new modules regime can only find files in the final modules
layout, so interdependent files can be built only if they're linked
first or have a strict dependency order provided to cmake. In many
cases the latter is impractical.

common/cmake_modules/GncAddSchemeTargets.cmake

@@ -174,6 +174,7 @@ function(gnc_add_scheme_targets _TARGET)
   endif()
 
   # If links are requested, we simply link (or copy, for Windows) each source file to the dest directory
+  set(TARGET_LINKS "")
   if(SCHEME_TGT_MAKE_LINKS)
     set(_LINK_DIR ${CMAKE_BINARY_DIR}/${GUILE_REL_UNIX_SITEDIR}/${SCHEME_TGT_OUTPUT_DIR})
     file(MAKE_DIRECTORY ${_LINK_DIR})
@@ -193,7 +194,8 @@ function(gnc_add_scheme_targets _TARGET)
         )
       endif()
     endforeach(scheme_file)
-    add_custom_target(${_TARGET}-links ALL DEPENDS ${_SCHEME_LINKS})
+    set(TARGET_LINKS ${_TARGET}-links)
+    add_custom_target(${TARGET_LINKS} ALL DEPENDS ${_SCHEME_LINKS})
   endif()
 
   # Construct the guile source and compiled load paths
@@ -279,7 +281,7 @@ function(gnc_add_scheme_targets _TARGET)
   if (__DEBUG)
     message("TARGET_FILES are ${_TARGET_FILES}")
   endif()
-  add_custom_target(${_TARGET} ALL DEPENDS ${_TARGET_FILES})
+  add_custom_target(${_TARGET} ALL DEPENDS ${_TARGET_FILES} ${TARGET_LINKS})
 
   set(_TARGET_FILES "${_TARGET_FILES}" PARENT_SCOPE)