Do the same in add_idl_reg_script() (currently unused helper) as well.
This is an addendum to commit b587e7b32, where the removal of the
IDL_FILE_FULL variable definition, broke dependency tracking with
the DEPENDS option. Now we use the correct variable.
The problem was caught after doing a partial (non-clean) build after
commit 0d10fb814. In this commit, two new interfaces, IExecuteCommand
and IObjectWithSelection, were added in the psdk/shobjidl.idl file
and used elsewhere. Recompilation correctly regenerated the corresponding
header, psdk/shobjidl.h, but did not trigger a regeneration of the uuid
static library (via the regeneration of sdk/lib/uuid/shobjidl_i.c),
due to broken dependency tracking on the shobjidl.idl file.
Because of this, the shobjidl_i.c did not contain the new GUID
definitions for these new interfaces, IID_IExecuteCommand and
IID_IObjectWithSelection, and triggered linking errors for the
com_apitest, actxprxy and shell32 modules:
```
error LNK2001: unresolved external symbol _IID_IExecuteCommand
error LNK2001: unresolved external symbol _IID_IObjectWithSelection
fatal error LNK1120: 2 unresolved externals
```
