These headers are not related to any Make rule but they do appear in
compiling of libreg.so, specifying .h files in compiler cmdline is flagged
as error by clang

| clang-4.0: error: cannot specify -o when generating multiple output files
| make: *** [libreg.so] Error 1

This is how we see headers in cmdline
-O2 -fpic -std=gnu
99 -Wall -Werror -pedantic -Wall -g -DUSE_GCRYPT -DCONFIG_LIBNL30 `pkg-config --cflags libnl-3.0`  -o libreg.so -shared -Wl,-soname,libreg.so
regdb.h reglib.h reglib.c keys-gcrypt.c -Wl,-O1 -Wl,--hash-style=gnu -Wl,--as-needed -L ./ -lm -lgcrypt

Signed-off-by: Khem Raj <raj.khem@gmail.com>

--- a/Makefile.kk	2016-11-15 04:54:53.338670000 +0000
+++ a/Makefile	2016-11-15 04:55:07.718670000 +0000
@@ -114,7 +114,7 @@ keys-%.c: utils/key2pub.py $(wildcard $(
 	$(NQ) '  Trusted pubkeys:' $(wildcard $(PUBKEY_DIR)/*.pem)
 	$(Q)./utils/key2pub.py --$* $(wildcard $(PUBKEY_DIR)/*.pem) $@
 
-$(LIBREG): regdb.h reglib.h reglib.c
+$(LIBREG): reglib.c
 	$(NQ) '  CC  ' $@
 	$(Q)$(CC) $(CFLAGS) $(CPPFLAGS) -o $@ -shared -Wl,-soname,$(LIBREG) $^ $(LDFLAGS) $(LIBREGLDLIBS)