Add entry for <TPLNAME>_LIB_ENABLED_DEPENDENCIES to build ref (TriBIT…

…SPub#63, TriBITSPub#299, TriBITSPub#494)

tribits/doc/build_ref/TribitsBuildReferenceBody.rst

@@ -1767,6 +1767,24 @@ libraries in the right order by configuring with::
 (where ``...`` are the rest of the libraries found in order).
 
 
+Adjusting upstream dependencies for a Third-Party Library (TPL)
+---------------------------------------------------------------
+
+Some TPLs have dependencies on one or more upstream TPLs.  These dependencies
+must be specified correctly for the compile and links to work correctly.  The
+<Project> Project already defines these dependencies for the average situation
+for all of these TPLs.  However, there may be situations where the
+dependencies may need to be tweaked to match how these TPLs were actually
+installed on some systems.  The dependencies for a TPL can be overridded by
+setting::
+
+  -D <TPLNAME>_LIB_ENABLED_DEPENDENCIES="<tpl_1>;<tpl_2>;..."
+
+If any of the specified TPLs are listed after ``<TPLNAME>`` in the
+``TPLsList.cmake`` file or are not enabled, then a configure-time error will
+occur.
+
+
 Disabling support for a Third-Party Library (TPL)
 --------------------------------------------------