doc: add src dir in build dir for gtkdoc-scan to parse enumerators
doc: add src dir in build dir for gtkdoc-scan to parse enumerators

At present, enumerators are not listed in auto-generated hinawa.types
file. This is a bit combersome to maintain the file in tree.

This commit adds src dir in build dir for the above.

takaswie/libhinawa,takaswie/libhinawa