This section contains strings specifying libraries to be added to the link by the linker.
The strings are encoded as standard null-terminated UTF-8 strings.
This patch adds a way to describe and dump SHT_LLVM_DEPENDENT_LIBRARIES sections.
I introduced a new YAMLFlowString type here. That used to teach obj2yaml to dump
them like:
```
Libraries: [ foo, bar ]
```
instead of the following (if StringRef would be used):
```
Libraries:
- foo
- bar
```
Differential revision: https://reviews.llvm.org/D70598
