This PR fixes two issues:
- First, in MSVC compiled binaries both the LLVM _and_ MSVC symbols are
present, but only the MSVC symbols have correct values. For example:
```
0:000> cdb: Reading initial command '.scriptload DumpCountersOld.js ; !dumpcounters "cov" ; q'
JavaScript script successfully loaded from 'DumpCountersOld.js'
[+] not disabling sympath
INFO: Seed: 58715679
INFO: Loaded 1 modules (3968 inline 8-bit counters): 3968 [00007FF70DB4B000, 00007FF70DB4BF80), # XXX Note
xxx.exe: Running 1 inputs 1 time(s) each.
Running: inp
[+] processing xxx.exe
[+] using LLVM 10 symbols - 0x7ff70db72b00:0x7ff70db72b08 # XXX These are wrong
```
This means the order we search for the coverage symbols is important.
- Secondly, this enables support for MSVC 8bit counter coverage.
## Validation Steps Performed
Running any recent MSVC compiled libfuzzer target should fail to actually collect coverage, instead just returning the 8 null bytes described in the linked issue.
