FindDoxygen: Escape backslashes in default values
Doxygen 1.8.15 added a new LATEX_MAKEINDEX_CMD config item and it has a default value that contains a backslash on some installations.
Fixes: #18738 (closed)
Doxygen 1.8.15 added a new LATEX_MAKEINDEX_CMD config item and it has a default value that contains a backslash on some installations.
Fixes: #18738 (closed)