Avoid MSBuild crash when DOTNET_SYSTEM_GLOBALIZATION_INVARIANT mode i…

…s enabled and console codepage, not ANSI. (#8738)

Context
If DOTNET_SYSTEM_GLOBALIZATION_INVARIANT is enabled and console codepage non-ANSI MSBuild will crash on an attempt to create CultureInfo:

Unhandled exception. System.Globalization.CultureNotFoundException: Only the invariant culture is supported in globalization-invariant mode. See https://aka.ms/GlobalizationInvariantMode for more information. (Parameter 'name')
en-US is an invalid culture identifier.
Changes Made
Keep the current thread culture the same if CurrentUICulture is Invariant.

src/MSBuild.UnitTests/XMake_Tests.cs

@@ -642,6 +642,30 @@ public void SetConsoleUICulture()
             thisThread.CurrentUICulture = originalUICulture;
         }
 
+        /// <summary>
+        /// We shouldn't change the UI culture if the current UI culture is invariant.
+        /// In other cases, we can get an exception on CultureInfo creation when System.Globalization.Invariant enabled.
+        /// </summary>
+
+        [Fact]
+        public void SetConsoleUICultureInInvariantCulture()
+        {
+            Thread thisThread = Thread.CurrentThread;
+
+            // Save the current UI culture, so we can restore it at the end of this unit test.
+            CultureInfo originalUICulture = thisThread.CurrentUICulture;
+
+            thisThread.CurrentUICulture = CultureInfo.InvariantCulture;
+            MSBuildApp.SetConsoleUI();
+
+            // Make sure we don't change culture.
+            thisThread.CurrentUICulture.ShouldBe(CultureInfo.InvariantCulture);
+
+            // Restore the current UI culture back to the way it was at the beginning of this unit test.
+            thisThread.CurrentUICulture = originalUICulture;
+        }
+
+
 #if FEATURE_SYSTEM_CONFIGURATION
         /// <summary>
         /// Invalid configuration file should not dump stack.

src/MSBuild/XMake.cs

@@ -1693,7 +1693,8 @@ internal static void SetConsoleUI()
                     &&
                     codepage != thisThread.CurrentUICulture.TextInfo.OEMCodePage
                     &&
-                    codepage != thisThread.CurrentUICulture.TextInfo.ANSICodePage)
+                    codepage != thisThread.CurrentUICulture.TextInfo.ANSICodePage
+                    && !Equals(CultureInfo.InvariantCulture, thisThread.CurrentUICulture))
             {
                 thisThread.CurrentUICulture = new CultureInfo("en-US");
                 return;