Re: ld/testsuite: adjust ld-arm to run shared tests only when supported

Re: ld/testsuite: adjust ld-arm to run shared tests only when supported

commit 67527cffcd enabled previously disabled tests unresolved-1-dyn,
thumb-plt and thumb-plt-got for nacl.  The first fails due to trying
to link against mixed-lib.so which isn't compiled for nacl.  The last
two fail with
objdump: tmpdir/dump(.rel.plt): relocation 0 has invalid symbol index 14885104
and
readelf: Error:  bad symbol index: 00e320f0 in reloc

Relocation section '.rel.plt' at offset 0x128 contains 1 entry:
 Offset     Info    Type                Sym. Value  Symbol's Name
e320f000  e320f000 R_ARM_NONE

	* testsuite/ld-arm/arm-elf.exp: Disable unresolved-1-dyn,
	thumb-plt and thumb-plt-got for nacl.