ld: Pass $NOPIE_CFLAGS and $NOPIE_LDFLAGS to even more ELF shared tests

Some distributions configure GCC with --enable-default-pie, so that it
defaults to compile with -fPIE and link with -pie, which is unexpected
by the test.  Therefore compile the non-PIC sources with $NOPIE_CFLAGS
and link the test programs with $NOPIE_LDFLAGS.

Commit 9d1c54ed7f3a ("Pass $NOPIE_CFLAGS and $NOPIE_LDFLAGS to more ELF
tests") added $NOPIE_CFLAGS when compiling sh1np.o.  It missed to add it
to sh2np.o and mainnp.o.

ld/testsuite/
	PR ld/21090
	* ld-shared/shared.exp (shared_test): Add support for optional
	ldflags argument and use it when linking the test program.
	(sh2np.o, mainnp.o): Compile with $NOPIE_CFLAGS.
	(shnp, shp, shmpnp, shmpp): Link with $NOPIE_LDFLAGS.

Fixes: 9d1c54ed7f3a ("Pass $NOPIE_CFLAGS and $NOPIE_LDFLAGS to more ELF tests")
Bug: https://sourceware.org/PR21090
Signed-off-by: Jens Remus <jremus@linux.ibm.com>