[lld] Do not emit dynamic relocations for .eh_frame section · Pull Request !203 · OpenHarmony/third_party_llvm-project

### Issue

https://gitee.com/openharmony/third_party_llvm-project/issues/I6QXQX?from=project-issue

### Reason (Purpose, Solved Problem)

Position-independent C++ binaries which use exceptions for mipsel-linux-ohos were not built properly. Without `-Wl,-z,notext` the following error occurred:

```
ld.lld: error: relocation R_MIPS_32 cannot be used against local symbol; recompile with -fPIC
```

With `-Wl,-z,notext` and `-Wl,--check-dynamic-relocations` the following error occurred:

```
ld.lld: error: out/exe:(.eh_frame+0x1cb): internal linker error: wrote incorrect addend value 0xE4C0000 instead of 0x32470 for dynamic relocation R_MIPS_REL32 at offset 0xC27 against symbol DW.ref.__gxx_personality_v0
```

There is a PR proposing a workaround on the issue by using PC-relative encodings instead of absolute ones when emitting object files https://gitee.com/openharmony/third_party_llvm-project/pulls/199. But we should be able to work with absolute-encoded pointers in object files as well since the bfd linker handles them correctly.

See the linked issue for details.

### Description

We re-write pointer encodings in .eh_frame section so they become pc-relative instead of absolute. That allows us to resolve the corresponding relocations statically (after changing the expr from `R_ABS` to `R_PC`), so there is no need in dynamic relocations and we do not emit them against read-only resulting .eh_frame section.

### Test (Local test)

Running `check-llvm` and `check-lld` does not produce any issues.

### Need to cherry-pick to release (eg：monthly_20221018, OpenHarmony-3.2-Beta5 ...) branch？

- [ ] yes，branch list:
- [x] no

why:

`mipsel-linux-ohos` target isn't used by any devices/boards in OHOS's master branch.

类型	指派人员	状态
审查	hhj Pavel Kosov	进行中 (0/1人)
测试	openharmony_ci	进行中 (0/1人)

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