pkgbase: fix inclusion of tests in ssh, bsnmp, clibs-dev

Currently, files that belong in the tests package are included in the
ssh, bsnmp, and clibs-dev packages:

ssh.plist
24:@dir(root,wheel,0755,) /usr/tests/secure/libexec
25:@(root,wheel,0444,) /usr/tests/secure/libexec/Kyuafile

bsnmp.plist
82:@dir(root,wheel,0755,) /usr/tests/lib/libbsnmp
83:@(root,wheel,0444,) /usr/tests/lib/libbsnmp/Kyuafile
84:@(root,wheel,0555,) /usr/tests/lib/libbsnmp/bsnmpd_test

clibs-dev.plist
2518:@dir(root,wheel,0755,) /usr/tests/lib/csu
2519:@(root,wheel,0444,) /usr/tests/lib/csu/Kyuafile

This is caused by the PACKAGE=foo assignment in foo/Makefile.inc which
overrides the default PACKAGE?=tests in bsd.test.mk.

To fix this, instead use PACKAGE?=foo in foo/Makefile.inc and set
PACKAGE=tests in foo/tests/Makefile.

PR:		249144
Reviewed by:	bapt, emaste
Sponsored by:	The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D47025

lib/csu/Makefile.inc

@@ -1,4 +1,4 @@
-PACKAGE=	clibs-dev
+PACKAGE?=	clibs-dev
 
 NO_WMISSING_VARIABLE_DECLARATIONS=
 # Can't instrument these files since that breaks non-sanitized programs.

lib/csu/tests/Makefile

@@ -1,3 +1,5 @@
+PACKAGE=	tests
+
 SUBDIR=		dso
 TESTS_SUBDIRS=	dynamic
 TESTS_SUBDIRS+=	dynamiclib

lib/libbsnmp/Makefile.inc

@@ -1,4 +1,4 @@
 INCSDIR=	${INCLUDEDIR}/bsnmp
-PACKAGE=	bsnmp
+PACKAGE?=	bsnmp
 
 .include "../Makefile.inc"

lib/libbsnmp/tests/Makefile

@@ -1,5 +1,7 @@
 .include <bsd.own.mk>
 
+PACKAGE=	tests
+
 ATF_TESTS_C+=	bsnmpd_test
 
 SRCS.bsmpd_test=	bsnmpd_test.c

secure/libexec/Makefile.inc

@@ -1,4 +1,4 @@
 BINDIR?=	/usr/libexec
-PACKAGE=	ssh
+PACKAGE?=	ssh
 
 .include "../Makefile.inc"

secure/libexec/tests/Makefile

@@ -1,4 +1,5 @@
 .PATH:		${SRCTOP}/tests
 KYUAFILE=	yes
+PACKAGE=	tests
 
 .include <bsd.test.mk>