Add stdout of compiler to OutputChannel

[yaner-here]

Some compilers (such as MSVC) will output logs to both stderr and stdout. Showing stdout could be helpful when troubleshooting.

PS C:\> cl.exe test.cpp /Fe: test.bin -D DEBUG -D CPH 1>stdout.txt 2> stderr.txt      


PS C:\> cat .\stderr.txt                       
Microsoft (R) C/C++ Optimizing Compiler Version 19.41.34120 for x64
Copyright (C) Microsoft Corporation. All rights reserved.


PS C:\> cat .\stdout.txt
test.cpp
c:\test.cpp: fatal error C1041: Unable to open program database "C:\Program Files\Microsoft VS Code\vc140.pdb"; if you want to write multiple CL.EXE to the same .PDB file, use /FS.