Update building instructions (#4650)

doc/building.md

@@ -1,29 +1,52 @@
 
-# How to build Openconsole
+# How to build OpenConsole
 
-Openconsole can be built with Visual Studio or from the command line. There are build scripts for both cmd and PowerShell in /tools.
+This repository uses [git submodules](https://git-scm.com/book/en/v2/Git-Tools-Submodules) for some of its dependencies. To make sure submodules are restored or updated, be sure to run the following prior to building:
+
+```shell
+git submodule update --init --recursive
+```
+
+OpenConsole.sln may be built from within Visual Studio or from the command-line using a set of convenience scripts & tools in the **/tools** directory:
 
 When using Visual Studio, be sure to set up the path for code formatting. This can be done in Visual Studio by going to Tools > Options > Text Editor > C++ > Formatting and checking "Use custom clang-format.exe file" and choosing the clang-format.exe in the repository at /dep/llvm/clang-format.exe by clicking "browse" right under the check box.
 
-## Building with cmd
+### Building in PowerShell
+
+```powershell
+Import-Module .\tools\OpenConsole.psm1
+Set-MsBuildDevEnvironment
+Invoke-OpenConsoleBuild
+```
+
+There are a few additional exported functions (look at their documentation for further details):
 
-The cmd scripts are set up to emulate a portion of the OS razzle build environment. razzle.cmd is the first script that should be run. bcz.cmd will build clean and bz.cmd should build incrementally.
+- `Invoke-OpenConsoleBuild` - builds the solution. Can be passed msbuild arguments.
+- `Invoke-OpenConsoleTests` - runs the various tests. Will run the unit tests by default.
+- `Start-OpenConsole` - starts Openconsole.exe from the output directory. x64 is run by default.
+- `Debug-OpenConsole` - starts Openconsole.exe and attaches it to the default debugger. x64 is run by default.
+- `Invoke-CodeFormat` - uses clang-format to format all c++ files to match our coding style.
+
+### Building in Cmd
+
+```shell
+.\tools\razzle.cmd
+bcz
+```
 
 There are also scripts for running the tests:
 - `runut.cmd` - run the unit tests
 - `runft.cmd` - run the feature tests
 - `runuia.cmd` - run the UIA tests
 - `runformat` - uses clang-format to format all c++ files to match our coding style.
 
-## Build with Powershell
+## Running & Debugging
 
-Openconsole.psm1 should be loaded with `Import-Module`. From there `Set-MsbuildDevEnvironment` will set up environment variables required to build. There are a few exported functions (look at their documentation for further details):
+To debug the Windows Terminal in VS, right click on `CascadiaPackage` (in the Solution Explorer) and go to properties. In the Debug menu, change "Application process" and "Background task process" to "Native Only".
 
-- `Invoke-OpenConsolebuild` - builds the solution. Can be passed msbuild arguments.
-- `Invoke-OpenConsoleTests` - runs the various tests. Will run the unit tests by default.
-- `Start-OpenConsole` - starts Openconsole.exe from the output directory. x64 is run by default.
-- `Debug-OpenConsole` - starts Openconsole.exe and attaches it to the default debugger. x64 is run by default.
-- `Invoke-CodeFormat` - uses clang-format to format all c++ files to match our coding style.
+You should then be able to build & debug the Terminal project by hitting <kbd>F5</kbd>.
+
+> 👉 You will _not_ be able to launch the Terminal directly by running the WindowsTerminal.exe. For more details on why, see [#926](https://github.com/microsoft/terminal/issues/926), [#4043](https://github.com/microsoft/terminal/issues/4043)
 
 ## Configuration Types