Since d6de1e1a71406c75a4ea4d5a2fe84289f07ea3a1, no attributes is quivalent to
setting attribute to false.
This is a preliminary commit for https://reviews.llvm.org/D99080
Generate types for global variables with "weak" attribute.
Keep allocation scope the same for both weak and non-weak
globals as ELF symbol table can determine whether a global
symbol is weak or not.
Differential Revision: https://reviews.llvm.org/D71162
