number_decimfmtprops.cpp has unaligned static memory
Description
The file has the following code:
We have a report that this causes a crash on ARM. The DecimalFormatProperties is being constructed into an unaligned char array, and the DecimalFormatProperties' MeasureUnit field assigns to an int32_t field in its ctor.
Possible fix: add alignas as follows:
Activity
The fix should be included in a maintenance release if we have a 62 maintenance release.
There is one other call site in my code where I did something similar; it is also missing the alignas. This should be fixed up at the same time:
https://github.com/unicode-org/icu/blob/master/icu4c/source/common/static_unicode_sets.cpp#L28
For reference, here is the site that caused the crash reports:
https://github.com/unicode-org/icu/blob/master/icu4c/source/i18n/number_decimfmtprops.cpp#L18
