rust: Fix up aarch64-linux bootstrap [PR106072]

rust: Fix up aarch64-linux bootstrap [PR106072]

Bootstrap fails on aarch64-linux and some other arches with:
.../gcc/rust/parse/rust-parse-impl.h: In member function ‘Rust::AST::ClosureParam Rust::Parser<ManagedTokenSource>::parse_closure_param() [with ManagedTokenSource = Rust::Lexer]’:
.../gcc/rust/parse/rust-parse-impl.h:8916:49: error: ‘this’ pointer is null [-Werror=nonnull]
The problem is that while say on x86_64-linux the side-effects in the
arguments are evaluated from last argument to first, on aarch64-linux
it is the other way around, from first to last.  The C++ I believe even
in C++17 makes the evaluation of those side-effects unordered
(indeterminately sequenced with no interleaving), so that is fine.
But, when the call in return statement is evaluated from first to
last, std::move (pattern) happens before pattern->get_locus () and
the former will make pattern (std::unique_ptr) a wrapper object around
nullptr, so dereferencing it later to call get_locus () on it is invalid.

2022-12-14  Jakub Jelinek  <jakub@redhat.com>

	PR rust/106072
	* parse/rust-parse-impl.h (parse_closure_param): Store
	pattern->get_locus () in a temporary before std::move (pattern) is
	invoked.