Merged PR 32193: Set OmniSharp run script to be executable

Backport of https://github.com/dotnet/installer/pull/16772 but had to be modified due to lack of API support in 6.0.

src/SourceBuild/tarball/content/test/Microsoft.DotNet.SourceBuild.SmokeTests/OmniSharpTests.cs

@@ -66,6 +66,7 @@ public class OmniSharpTests : SmokeTests
 
             Directory.CreateDirectory(OmniSharpDirectory);
             ExecuteHelper.ExecuteProcessValidateExitCode("tar", $"xzf {omniSharpTarballFile} -C {OmniSharpDirectory}", OutputHelper);
+			ExecuteHelper.ExecuteProcessValidateExitCode("chmod", $"+x {OmniSharpDirectory}/run", OutputHelper);
         }
     }
 }