PR libstdc++/81706
	* attribs.c (attribute_value_equal): Use omp_declare_simd_clauses_equal
	for comparison of OMP_CLAUSEs regardless of flag_openmp{,_simd}.
	(duplicate_one_attribute, copy_attributes_to_builtin): New functions.
	* attribs.h (duplicate_one_attribute, copy_attributes_to_builtin): New
	declarations.

	* c-decl.c (merge_decls): Copy "omp declare simd" attributes from
	newdecl to corresponding __builtin_ if any.

	* decl.c (duplicate_decls): Copy "omp declare simd" attributes from
	newdecl to corresponding __builtin_ if any.

	* gcc.target/i386/pr81706.c: New test.
	* g++.dg/ext/pr81706.C: New test.

From-SVN: r254069