A crash was happening when both ObjC Category Merging and Relative
method lists were enabled.
ObjC Category Merging creates new data sections and adds them by calling
`addInputSection`. `addInputSection` uses the symbols within the added
section to determine which container to actually add the section to.
The issue is that ObjC Category merging is calling `addInputSection`
before actually adding the relevant symbols the the added section. This
causes `addInputSection` to add the `InputSection` to the wrong
container, eventually resulting in a crash.
To fix this, we ensure that ObjC Category Merging calls
`addInputSection` only after the symbols have been added to the
`InputSection`.
(cherry picked from commit 0df91893efc752a76c7bbe6b063d66c8a2fa0d55)
40b0764101