PMI failure log often includes no useful information about failures

eg:
```
jit-diff diff --pmi --diff
Using --output D:\repos\coreclr\bin\diffs
Using --diff D:\repos\coreclr\bin\Product\Windows_NT.x64.Checked
Using --arch x64
Using --core_root D:\repos\coreclr\bin\tests\Windows_NT.x64.Checked\Tests\Core_Root

Warning: it is best practice to use a Release build for --core_root, --crossgen, and --test_root.

No assemblies specified; defaulting to corelib
Beginning PMI Diffs for System.Private.CoreLib.dll
/ Finished 0/0 Base 0/1 Diff [5.9 sec]Error running D:\repos\coreclr\bin\tests\Windows_NT.x64.Checked\Tests\Core_Root\corerun.exe on D:\repos\coreclr\bin\tests\Windows_NT.x64.Checked\Tests\Core_Root\System.Private.CoreLib.dll
1 errors compiling set.
Dasm command "jit-dasm-pmi --platform D:\repos\coreclr\bin\tests\Windows_NT.x64.Checked\Tests\Core_Root --corerun D:\repos\coreclr\bin\tests\Windows_NT.x64.Checked\Tests\Core_Root\corerun.exe --jit D:\repos\coreclr\bin\Product\Windows_NT.x64.Checked\clrjit.dll --nocopy --output D:\repos\coreclr\bin\diffs\dasmset_1\diff D:\repos\coreclr\bin\tests\Windows_NT.x64.Checked\Tests\Core_Root\System.Private.CoreLib.dll" returned with 1 failures
| Finished 0/0 Base 1/1 Diff [5.9 sec]
Dasm commands returned 0 base failures, 1 diff failures.
Completed PMI Diffs for System.Private.CoreLib.dll in 5.92s
Diffs (if any) can be viewed by comparing: D:\repos\coreclr\bin\diffs\dasmset_1\base D:\repos\coreclr\bin\diffs\dasmset_1\diff

Warning: Failures detected generating asm: 0 base, 1 diff
```
has failure log:
```
Failed PREPALL on D:\repos\coreclr\bin\tests\Windows_NT.x64.Checked\Tests\Core_Root\System.Private.CoreLib.dll
```