Add -fdata-section support to cranelift-object

[bjorn3]

Feature

This is the data object counterpart to #2218.

Benefit

Same as per_function_sections. From the description of #2218:

This makes it possible for the linker to omit unused functions when --gc-sections is passed.

For cg_clif the executable size savings are quite big. One example is 26MB when a single .text section is used, but 15MB when a single section for each function is used, which is the same as when compiled using cg_llvm. I will probably disable this in debug mode though as it significantly increases the linking time.

Implementation

Similar to #2218

Alternatives

N/A