Use rcrt1.o%s/grcrt1.o%s to relocate static PIE

crt1.o is used to create dynamic and non-PIE static executables.  Static
PIE needs to link with rcrt1.o, instead of crt1.o, which is also used by
musl libc and OpenBSD:

https://gcc.gnu.org/ml/gcc/2015-06/msg00008.html

to relocate static PIE at run-time.  When -pg is used with -static-pie,
grcrt1.o should be used.

	* config/gnu-user.h (GNU_USER_TARGET_STARTFILE_SPEC): Use
	rcrt1.o%s/grcrt1.o%s for -static-pie.

From-SVN: r254890