testsuite: Require ucn in g++.dg/cpp0x/udlit-extended-id-1.C

testsuite: Require ucn in g++.dg/cpp0x/udlit-extended-id-1.C

g++.dg/cpp0x/udlit-extended-id-1.C FAILs on Solaris/SPARC and x86 with
the native assembler:

UNRESOLVED: g++.dg/cpp0x/udlit-extended-id-1.C  -std=c++14 compilation failed to produce executable
FAIL: g++.dg/cpp0x/udlit-extended-id-1.C  -std=c++17 (test for excess errors)
UNRESOLVED: g++.dg/cpp0x/udlit-extended-id-1.C  -std=c++17 compilation failed to produce executable
FAIL: g++.dg/cpp0x/udlit-extended-id-1.C  -std=c++20 (test for excess errors)
UNRESOLVED: g++.dg/cpp0x/udlit-extended-id-1.C  -std=c++20 compilation failed to produce executable

/bin/as doesn't support UCN identifiers:

/usr/ccs/bin/as: "/var/tmp//ccCl_9fa.s", line 4: error: invalid character (0xcf)
/usr/ccs/bin/as: "/var/tmp//ccCl_9fa.s", line 4: error: invalid character (0x80)
/usr/ccs/bin/as: "/var/tmp//ccCl_9fa.s", line 4: error: statement syntax
/usr/ccs/bin/as: "/var/tmp//ccCl_9fa.s", line 4: error: statement syntax
[...]

To avoid this, this patch requires ucn support.

Tested on i386-pc-solaris2.11 (as and gas), sparc-sun-solaris2.11 (as
and gas), and i686-pc-linux-gnu.

2024-01-30  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>

	gcc/testsuite:
	* g++.dg/cpp0x/udlit-extended-id-1.C: Require ucn support.