Exec: stop setting a locale on Unix.

src/Tasks.UnitTests/Exec_Tests.cs

@@ -69,6 +69,42 @@ public void EscapeSpecifiedCharactersInPathToGeneratedBatchFile()
             }
         }
 
+        [UnixOnlyTheory]
+        [InlineData(true)]
+        [InlineData(false)]
+        public void ExecSetsLocaleOnUnix(bool enableChangeWave)
+        {
+            using (var env = TestEnvironment.Create())
+            {
+                env.SetEnvironmentVariable("LANG", null);
+                env.SetEnvironmentVariable("LC_ALL", null);
+
+                if (enableChangeWave)
+                {
+                    ChangeWaves.ResetStateForTests();
+                    // Important: use the version here
+                    env.SetEnvironmentVariable("MSBUILDDISABLEFEATURESFROMVERSION", ChangeWaves.Wave17_10.ToString());
+                    BuildEnvironmentHelper.ResetInstance_ForUnitTestsOnly();
+                }
+
+                Exec exec = PrepareExec("echo LANG=$LANG; echo LC_ALL=$LC_ALL;");
+                bool result = exec.Execute();
+                Assert.True(result);
+
+                MockEngine engine = (MockEngine)exec.BuildEngine;
+                if (enableChangeWave)
+                {
+                    engine.AssertLogContains("LANG=en_US.UTF-8");
+                    engine.AssertLogContains("LC_ALL=en_US.UTF-8");
+                }
+                else
+                {
+                    engine.AssertLogDoesntContain("LANG=en_US.UTF-8");
+                    engine.AssertLogDoesntContain("LC_ALL=en_US.UTF-8");
+                }
+            }
+        }
+
         /// <summary>
         /// Ensures that calling the Exec task does not leave any extra TEMP files
         /// lying around.

src/Tasks/Exec.cs

@@ -591,7 +591,12 @@ protected internal override void AddCommandLineCommands(CommandLineBuilderExtens
             {
                 commandLine.AppendSwitch("-c");
                 commandLine.AppendTextUnquoted(" \"");
-                commandLine.AppendTextUnquoted("export LANG=en_US.UTF-8; export LC_ALL=en_US.UTF-8; . ");
+                bool setLocale = !ChangeWaves.AreFeaturesEnabled(ChangeWaves.Wave17_10);
+                if (setLocale)
+                {
+                    commandLine.AppendTextUnquoted("export LANG=en_US.UTF-8; export LC_ALL=en_US.UTF-8; ");
+                }
+                commandLine.AppendTextUnquoted(". ");
                 commandLine.AppendFileNameIfNotNull(batchFileForCommandLine);
                 commandLine.AppendTextUnquoted("\"");
             }