[clang] Add back -fsanitize=array-bounds workaround for size-1 array after...

[clang] Add back -fsanitize=array-bounds workaround for size-1 array after -fstrict-flex-arrays change

Before C99 introduced flexible array member, common practice uses size-1 array
to emulate FAM, e.g. https://github.com/python/cpython/issues/94250
As a result, -fsanitize=array-bounds instrumentation skipped such structures
as a workaround (from 539e4a77).

D126864 accidentally dropped the workaround. Add it back with tests.