Build system: Non-dtrace distcheck hacks

automake 1.10 really wants foo.c for foo.O, so give it some dummy files to
deal with if it really needs them.

dix/Makefile.am

@@ -57,3 +57,8 @@ noinst_PROGRAMS = dix.O
 dix.O: dtrace-dix.o $(am_libdix_la_OBJECTS)
 	ld -r -o $@ .libs/*.o
 endif
+
+dix.c:
+	touch $@
+
+CLEANFILES = dix.c

os/Makefile.am

@@ -59,5 +59,9 @@ noinst_PROGRAMS = os.O
 
 os.O: dtrace.o $(am_libos_la_OBJECTS)
 	ld -r -o $@ dtrace.o .libs/*.o
-
 endif
+
+os.c:
+	touch $@
+
+CLEANFILES = os.c