[3.11] gh-110190: Fix ctypes structs with array on Arm (#112604) #112766
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Set MAX_STRUCT_SIZE to 32 in stgdict.c when on Arm platforms. This because on Arm platforms structs with at most 4 elements of any floating point type values can be passed through registers. If the type is double the maximum size of the struct is 32 bytes. On x86-64 Linux, it's maximum 16 bytes hence we need to differentiate.
(cherry picked from commit bc68f4a)