build: ensure we remove the newly generated *eo.legacy.c files for distcheck

Eolain now generates extra files for the C legacy implementations and
distcheck has trouble with them not being removed by the build system.

Going to handle lists of them in all the different makefiles (elm,
ecore, emotion, etc) would be a lot extra work. Thus I will just make
sure the get removed during our clean-local rule.

Given 1.22 is the last release we will use autotools for I think this is
a fair compromise to get this fixed.

Differential Revision: https://phab.enlightenment.org/D8052

Makefile.am

@@ -519,6 +519,7 @@ pkgbuild::
 
 clean-local:
 	rm -rf benchmark coverage
+	@find . -name '*eo.legacy.c' -delete
 
 DISTCLEANFILES= \
 ./src/lib/emile/Makefile \