*: add INSERTs to *.src files where appropriate

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/mailutils/Kbuild.src b/mailutils/Kbuild.src
index 871e879..b2fb735 100644
--- a/mailutils/Kbuild.src
+++ b/mailutils/Kbuild.src
@@ -5,6 +5,8 @@
 # Licensed under the GPL v2, see the file LICENSE in this tarball.
 
 lib-y:=
+
+INSERT
 lib-$(CONFIG_MAKEMIME)     += mime.o mail.o
 lib-$(CONFIG_POPMAILDIR)   += popmaildir.o mail.o
 lib-$(CONFIG_REFORMIME)    += mime.o mail.o