Add C startup code tests for PIE binaries.

- Force dynamic to be a non-PIE binary.

- Add a dynamicpie test which uses a PIE binary.

Reviewed by:	andrew
Obtained from:	CheriBSD
MFC after:	2 weeks
Sponsored by:	DARPA
Differential Revision:	https://reviews.freebsd.org/D27127

lib/csu/tests/Makefile

@@ -3,6 +3,7 @@
 SUBDIR=		dso
 TESTS_SUBDIRS=	dynamic
 TESTS_SUBDIRS+=	dynamiclib
+TESTS_SUBDIRS+=	dynamicpie
 TESTS_SUBDIRS+=	static
 
 SUBDIR_DEPEND_dynamiclib=dso

lib/csu/tests/dynamic/Makefile

@@ -2,5 +2,8 @@
 
 .PATH: ${.CURDIR:H}
 
+.include <src.opts.mk>
+MK_PIE=	no
+
 .include "../Makefile.tests"
 .include <bsd.test.mk>

lib/csu/tests/dynamicpie/Makefile

@@ -0,0 +1,9 @@
+# $FreeBSD$
+
+.PATH: ${.CURDIR:H}
+
+.include <src.opts.mk>
+MK_PIE=	yes
+
+.include "../Makefile.tests"
+.include <bsd.test.mk>