Cilk Plus testsuite needs massive cleanup (PR testsuite/70595)

	gcc:
	PR testsuite/70595
	* doc/sourcebuild.texi (Effective-Target Keywords, Other
	attributes): Document cilkplus_runtime.

	gcc/testsuite:
	PR testsuite/70595
	* lib/target-supports.exp (check_libcilkrts_available): Rename to ...
	(check_effective_target_cilkplus_runtime): ... this.
	* g++.dg/cilk-plus/cilk-plus.exp: Adapt to it.
	* gcc.dg/cilk-plus/cilk-plus.exp: Likewise.

	* c-c++-common/cilk-plus/CK/cilk-for-2.c: Remove dg-do target selector.
	Require cilkplus_runtime.
	Don't add -lcilkrts.
	* c-c++-common/cilk-plus/CK/cilk-fors.c: Likewise.
	* c-c++-common/cilk-plus/CK/cilk_for_grain.c: Likewise.
	* c-c++-common/cilk-plus/CK/cilk_for_ptr_iter.c: Likewise.
	* c-c++-common/cilk-plus/CK/fib.c: Likewise.
	* c-c++-common/cilk-plus/CK/fib_init_expr_xy.c: Likewise.
	* c-c++-common/cilk-plus/CK/fib_no_return.c: Likewise.
	* c-c++-common/cilk-plus/CK/fib_no_sync.c: Likewise.
	* c-c++-common/cilk-plus/CK/nested_cilk_for.c: Likewise.
	* c-c++-common/cilk-plus/CK/pr60586.c: Likewise.
	* c-c++-common/cilk-plus/CK/pr69826-1.c: Likewise.
	* c-c++-common/cilk-plus/CK/pr69826-2.c: Likewise.
	* c-c++-common/cilk-plus/CK/spawnee_inline.c: Likewise.
	* c-c++-common/cilk-plus/CK/spawner_inline.c: Likewise.
	* c-c++-common/cilk-plus/CK/spawning_arg.c: Likewise.
	* c-c++-common/cilk-plus/CK/steal_check.c: Likewise.
	* c-c++-common/cilk-plus/CK/varargs_test.c: Likewise.
	* g++.dg/cilk-plus/CK/catch_exc.cc: Likewise.
	* g++.dg/cilk-plus/CK/cilk-for-tplt.cc: Likewise.
	* g++.dg/cilk-plus/CK/const_spawn.cc: Likewise.
	* g++.dg/cilk-plus/CK/fib-opr-overload.cc: Likewise.
	* g++.dg/cilk-plus/CK/fib-tplt.cc: Likewise.
	* g++.dg/cilk-plus/CK/for1.cc: Likewise.
	* g++.dg/cilk-plus/CK/lambda_spawns.cc: Likewise.
	* g++.dg/cilk-plus/CK/lambda_spawns_tplt.cc: Likewise.
	* g++.dg/cilk-plus/CK/pr60586.cc: Likewise.
	* g++.dg/cilk-plus/CK/pr66326.cc: Likewise.
	* g++.dg/cilk-plus/CK/stl_iter.cc: Likewise.
	* g++.dg/cilk-plus/CK/stl_rev_iter.cc: Likewise.
	* g++.dg/cilk-plus/CK/stl_test.cc: Likewise.

	* c-c++-common/cilk-plus/CK/pr63307.c: Remove dg-do target selector.
	* c-c++-common/cilk-plus/SE/ef_error3.c: Likewise.

	* c-c++-common/cilk-plus/SE/ef_error2.c: Explain target selector.

	* c-c++-common/cilk-plus/CK/test__cilk.c: Run if
	cilkplus_runtime.

From-SVN: r235574