Fix this test on Linux

Author: mxcl

Tests/Build/DescribeTests.swift

@@ -23,3 +23,12 @@ final class DescribeTests: XCTestCase {
         }
     }
 }
+
+
+extension DescribeTests: XCTestCaseProvider {
+    var allTests: [(String, () throws -> Void)] {
+        return [
+            ("testDescribingNoModulesThrows", testDescribingNoModulesThrows),
+        ]
+    }
+}

Tests/LinuxMain.swift

@@ -12,6 +12,7 @@ import XCTest
 @testable import ManifestParsertest
 @testable import PackageDescriptiontest
 @testable import PackageTypetest
+@testable import Buildtest
 
 XCTMain([
     DependencyResolutionTestCase(),