ARM32 compilation fixes with GCC (dotnet/coreclr#27795)

ARM32 compilation fixes with GCC (dotnet/coreclr#27795)

* Suppress on clang only

* Fix integer conversion

* Extra qualifier

* Suppress warning

* Extra qualifier

* Signedness issues

* Correct offsetof

* Offsetof doesn't support non-constant values

* Conversion errors

* Move the comment too

* Fix assembly warning

* size is not constant

* Fix comment type

* Fix endmacro name

* Use OFFSET_NONE constant

Commit migrated from https://github.com/dotnet/coreclr/commit/e8bbcf18be67b864d16e12c13d16f1bea4a9c76e