Make timeout configurable

Author: rolfbjarne

tests/common/DotNet.cs

@@ -262,7 +262,14 @@ public static ExecutionResult Execute (string verb, string project, Dictionary<s
 				env ["MSBuildSDKsPath"] = null;
 				env ["MSBUILD_EXE_PATH"] = null;
 				var output = new StringBuilder ();
-				timeout ??= TimeSpan.FromMinutes (10);
+				if (timeout is null) {
+					var timeoutVar = Environment.GetEnvironmentVariable ("TIMEOUT_IN_MINUTES");
+					if (int.TryParse (timeoutVar, out var timeoutValue)) {
+						timeout = TimeSpan.FromMinutes (timeoutValue);
+					} else {
+						timeout = TimeSpan.FromMinutes (10);
+					}
+				}
 				var rv = Execution.RunWithStringBuildersAsync (Executable, args, env, output, output, Console.Out, workingDirectory: Path.GetDirectoryName (project), timeout: timeout).Result;
 				if (assert_success && rv.ExitCode != 0) {
 					var outputStr = output.ToString ();