Disable shorten 64 to 32 error for arm64 (do not make it fatal)

[andy31415]

Arm64 builds like ./scripts/build/build_examples.py --target linux-arm64-light-rpc-ipv6only-clang build were failing because pigweed casting errors in pw_tokenizer and pw_rpc.

Since pigweed updates take a bit (need some build system updates after the 1.0 freeze), I am disabling these errors for linux+arm64 (but we keep them for other platforms, so hopefully we keep having good code).

Fixes #23238

[github-actions]

PR #23237: Size comparison from b9cf4b9 to 6e5ded9

Decreases (2 builds for bl702)

platform	target	config	section	b9cf4b9	6e5ded9	change	% change
bl702	lighting-app	bl702	.debug_info	37908963	37908962	-1	-0.0
			.text	957316	957314	-2	-0.0
		bl702+rpc	.debug_info	41815578	41815576	-2	-0.0
			.text	1030762	1030758	-4	-0.0

Full report (7 builds for bl702, k32w, qpg)

platform	target	config	section	b9cf4b9	6e5ded9	change	% change
bl702	lighting-app	bl702		0	0	0	0.0
			(read only)	3262	3262	0	0.0
			(read/write)	1188963	1188963	0	0.0
			.bleromro	6296	6296	0	0.0
			.bleromrw	124	124	0	0.0
			.boot2	688	688	0	0.0
			.bss	67118	67118	0	0.0
			.bss_psram	29696	29696	0	0.0
			.comment	48	48	0	0.0
			.data	4272	4272	0	0.0
			.debug_abbrev	1507098	1507098	0	0.0
			.debug_aranges	133144	133144	0	0.0
			.debug_frame	486648	486648	0	0.0
			.debug_info	37908963	37908962	-1	-0.0
			.debug_line	5257455	5257455	0	0.0
			.debug_loc	3367679	3367679	0	0.0
			.debug_ranges	359456	359456	0	0.0
			.debug_str	3457927	3457927	0	0.0
			.hbn	509	509	0	0.0
			.hbn_noinit	260	260	0	0.0
			.init	342	342	0	0.0
			.init_array	144	144	0	0.0
			.psram	0	0	0	0.0
			.riscv.attributes	47	47	0	0.0
			.rodata	116744	116744	0	0.0
			.rsvd	3188	3188	0	0.0
			.shstrtab	293	293	0	0.0
			.stack	2048	2048	0	0.0
			.strtab	565127	565127	0	0.0
			.symtab	171680	171680	0	0.0
			.tcm_data	36	36	0	0.0
			.tcmcode	3262	3262	0	0.0
			.text	957316	957314	-2	-0.0
		bl702+rpc		0	0	0	0.0
			(read only)	3262	3262	0	0.0
			(read/write)	1284627	1284627	0	0.0
			.bleromro	6296	6296	0	0.0
			.bleromrw	124	124	0	0.0
			.boot2	688	688	0	0.0
			.bss	75166	75166	0	0.0
			.bss_psram	29936	29936	0	0.0
			.comment	48	48	0	0.0
			.data	4800	4800	0	0.0
			.debug_abbrev	1644643	1644643	0	0.0
			.debug_aranges	140648	140648	0	0.0
			.debug_frame	512020	512020	0	0.0
			.debug_info	41815578	41815576	-2	-0.0
			.debug_line	5631986	5631986	0	0.0
			.debug_loc	3560326	3560326	0	0.0
			.debug_ranges	381912	381912	0	0.0
			.debug_str	3853897	3853897	0	0.0
			.hbn	509	509	0	0.0
			.hbn_noinit	260	260	0	0.0
			.init	342	342	0	0.0
			.init_array	160	160	0	0.0
			.psram	0	0	0	0.0
			.riscv.attributes	47	47	0	0.0
			.rodata	130136	130136	0	0.0
			.rsvd	3188	3188	0	0.0
			.shstrtab	293	293	0	0.0
			.stack	2048	2048	0	0.0
			.strtab	624300	624300	0	0.0
			.symtab	189488	189488	0	0.0
			.tcm_data	36	36	0	0.0
			.tcmcode	3262	3262	0	0.0
			.text	1030762	1030758	-4	-0.0
k32w	contact	k32w0+release	(read/write)	661284	661284	0	0.0
			.bss	77040	77040	0	0.0
			.data	2104	2104	0	0.0
			.text	563028	563028	0	0.0
	light	k32w0+release	(read/write)	671496	671496	0	0.0
			.bss	74840	74840	0	0.0
			.data	2060	2060	0	0.0
			.text	591868	591868	0	0.0
	lock	k32w0+release	(read/write)	633092	633092	0	0.0
			.bss	75600	75600	0	0.0
			.data	2080	2080	0	0.0
			.text	552684	552684	0	0.0
qpg	lighting-app	qpg6105+debug	(read/write)	1148824	1148824	0	0.0
			.bss	110580	110580	0	0.0
			.data	832	832	0	0.0
			.text	595924	595924	0	0.0
	lock-app	qpg6105+debug	(read/write)	1113712	1113712	0	0.0
			.bss	106372	106372	0	0.0
			.data	836	836	0	0.0
			.text	560808	560808	0	0.0

[andy31415]

fast track after approx 1day because this fixes a build failure.