Removed @abs_top_builddir@ from doxygen.conf.in where it hampered reproducibe build

doc/doxygen.conf.in

@@ -54,7 +54,7 @@ PROJECT_LOGO           =
 # If a relative path is entered, it will be relative to the location
 # where doxygen was started. If left blank the current directory will be used.
 
-OUTPUT_DIRECTORY       = @abs_top_builddir@
+OUTPUT_DIRECTORY       = 
 
 # If the CREATE_SUBDIRS tag is set to YES, then doxygen will create
 # 4096 sub-directories (in 2 levels) under the output directory of each output
@@ -1477,18 +1477,6 @@ GENERATE_XML           = NO
 
 XML_OUTPUT             = xml
 
-# The XML_SCHEMA tag can be used to specify an XML schema,
-# which can be used by a validating XML parser to check the
-# syntax of the XML files.
-
-XML_SCHEMA             =
-
-# The XML_DTD tag can be used to specify an XML DTD,
-# which can be used by a validating XML parser to check the
-# syntax of the XML files.
-
-XML_DTD                =
-
 # If the XML_PROGRAMLISTING tag is set to YES Doxygen will
 # dump the program listings (including syntax highlighting
 # and cross-referencing information) to the XML output. Note that