[Doxygen] Fix bug in mk_api_doc.py where the generated

doxygen configuration would not point at the correct path to
the temporary directory.

doc/mk_api_doc.py

@@ -119,6 +119,7 @@ try:
     # Create configuration file from template
     doxygen_config_substitutions = {
         'OUTPUT_DIRECTORY': OUTPUT_DIRECTORY,
+        'TEMP_DIR': TEMP_DIR
     }
     doxygen_config_file = temp_path('z3api.cfg')
     configure_file('z3api.cfg.in', doxygen_config_file, doxygen_config_substitutions)

doc/z3api.cfg.in

@@ -684,7 +684,7 @@ WARN_LOGFILE           =
 INPUT                  = ../src/api/dotnet \
                          ../src/api/java \
                          ../src/api/c++ \
-                         ./tmp
+                         @TEMP_DIR@
 
 # This tag can be used to specify the character encoding of the source files
 # that doxygen parses. Internally doxygen uses the UTF-8 encoding, which is