Add behavior info for Environment.FailFast on non-Windows systems (#9490)

Author: ascpixi

xml/System/Environment.xml

@@ -547,7 +547,7 @@ Invalid argument
         <AssemblyVersion>4.2.0.0</AssemblyVersion>
       </AssemblyInfo>
       <Docs>
-        <summary>Immediately terminates a process after writing a message to the Windows Application event log, and then includes the message and optional exception information in error reporting to Microsoft.</summary>
+        <summary>Immediately terminates the process before reporting an error message. For Windows, the error message is written to the Windows Application event log, and the message and optional exception information is included in error reporting to Microsoft. For Unix-like systems, the message, alongside the stack trace, is written to the standard error stream.</summary>
       </Docs>
     </MemberGroup>
     <Member MemberName="FailFast">
@@ -608,23 +608,23 @@ Invalid argument
       </Parameters>
       <Docs>
         <param name="message">A message that explains why the process was terminated, or <see langword="null" /> if no explanation is provided.</param>
-        <summary>Immediately terminates a process after writing a message to the Windows Application event log, and then includes the message in error reporting to Microsoft.</summary>
+        <summary>Immediately terminates the process before reporting an error message. For Windows, the error message is written to the Windows Application event log, and the message is included in error reporting to Microsoft. For Unix-like systems, the message, alongside the stack trace, is written to the standard error stream.</summary>
         <remarks>
           <format type="text/markdown"><![CDATA[
 
 ## Remarks
  This method terminates a process without running any active `try`/`finally` blocks or finalizers.
 
- The `Environment.FailFast` method writes the `message` string to the Windows Application event log, creates a dump of your application, and then terminates the current process. The `message` string is also included in error reporting to Microsoft.
+ On Windows, the `Environment.FailFast` method writes the `message` string to the Windows Application event log, creates a dump of your application, and then terminates the current process. The `message` string is also included in error reporting to Microsoft via Windows Error Reporting. For more information, see [Windows Error Reporting: Getting Started](/windows-hardware/drivers/dashboard/).
+ 
+ On Unix-like systems, the message is written to the standard error stream, alongside the stack trace information.
 
  Use the `Environment.FailFast` method instead of the <xref:System.Environment.Exit%2A> method to terminate your application if the state of your application is damaged beyond repair, and executing your application's `try`/`finally` blocks and finalizers will corrupt program resources.
 
- Information is reported to Microsoft by using Windows Error Reporting. For more information, see [Windows Error Reporting: Getting Started](/windows-hardware/drivers/dashboard/).
-
 Calling the `Environment.FailFast` method to terminate execution of an application running in the Visual Studio debugger throws an <xref:System.ExecutionEngineException> and automatically triggers the [fatalExecutionEngineError managed debugging assistant (MDA)](/dotnet/framework/debug-trace-profile/fatalexecutionengineerror-mda).
 
 ## Examples
- The following example writes a log entry to the Windows Application event log and terminates the current process.
+ The following example writes a log entry to the Windows Application event log when running under Windows, or writes the error message to the standard error stream when running under a Unix-like system, and terminates the current process.
 
  :::code language="csharp" source="~/snippets/csharp/System/Environment/FailFast/ff.cs" id="Snippet1":::
  :::code language="fsharp" source="~/snippets/fsharp/System/Environment/FailFast/ff.fs" id="Snippet1":::
@@ -693,16 +693,18 @@ Calling the `Environment.FailFast` method to terminate execution of an applicati
       <Docs>
         <param name="message">A message that explains why the process was terminated, or <see langword="null" /> if no explanation is provided.</param>
         <param name="exception">An exception that represents the error that caused the termination. This is typically the exception in a <see langword="catch" /> block.</param>
-        <summary>Immediately terminates a process after writing a message to the Windows Application event log, and then includes the message and exception information in error reporting to Microsoft.</summary>
+        <summary>Immediately terminates the process before reporting an error message. For Windows, the error message is written to the Windows Application event log, and the message and exception information is included in error reporting to Microsoft. For Unix-like systems, the message alongside the stack trace is written to the standard error stream.</summary>
         <remarks>
           <format type="text/markdown"><![CDATA[
 
 ## Remarks
  This method terminates the process without running any active `try`/`finally` blocks or finalizers.
 
- The `Environment.FailFast` method writes the `message` string to the Windows Application event log, creates a dump of your application, and then terminates the current process.
+ On Windows, the `Environment.FailFast` method writes the `message` string to the Windows Application event log, creates a dump of your application, and then terminates the current process.
 
  Information is reported to Microsoft by using Windows Error Reporting. For more information, see [Windows Error Reporting: Getting Started](/windows-hardware/drivers/dashboard/). Error reporting to Microsoft includes `message` and `exception` information, which provides details used to classify the error. Although `exception` is not handled because the process is terminated, the contextual information that raised the exception is still obtained.
+ 
+ On Unix-like systems, the message is written to the standard error stream, alongside the stack trace information.
 
  If `exception` is `null`, or if `exception` is not thrown, this method operates the same as the <xref:System.Environment.FailFast%28System.String%29> method overload.