Merge pull request #30142 from jaredpar/fix-ftb

Correct unix first time build instructions

build/scripts/obtain_dotnet.sh

@@ -5,6 +5,8 @@
 # Source this script to ensure dotnet is installed and on the path.
 # If the FORCE_DOWNLOAD environment variable is set to "true", the system's dotnet install is ignored,
 # and dotnet is downloaded and installed locally.
+set -e
+set -u
 
 # This is a function to keep variable assignments out of the parent script (that is sourcing this file)
 install_dotnet () {

docs/contributing/Building, Debugging, and Testing on Unix.md

@@ -3,7 +3,7 @@ This guide is meant to help developers setup an environment for debugging / cont
 Particularly for developers who aren't experienced with .NET Core development on Linux. 
 
 ## Working with the code
-1. Install the [.NET Core SDK](https://www.microsoft.com/net/download/core)
+1. Ensure the commands `git` and `curl` are available
 1. Clone git@github.com:dotnet/roslyn.git
 1. Run `./build.sh --restore`
 1. Run `./build.sh --build`