Add windows to the list of available OS's in sdk tests

Makes the tests more realistic as they cover what happens when an sdk
OS specific variant is disabled (Windows is disabled by default). This
will allow issues around disabled variants to be detected early during
Soong bootstrapping.

Test: m nothing
Change-Id: I7ec47dbca52e38750166d755daf706aadea12d15

sdk/testing.go

@@ -61,6 +61,12 @@ func testSdkContext(bp string, fs map[string][]byte) (*android.TestContext, andr
 
 	config := android.TestArchConfig(buildDir, nil, bp, mockFS)
 
+	// Add windows as a default disable OS to test behavior when some OS variants
+	// are disabled.
+	config.Targets[android.Windows] = []android.Target{
+		{android.Windows, android.Arch{ArchType: android.X86_64}, android.NativeBridgeDisabled, "", ""},
+	}
+
 	ctx := android.NewTestArchContext()
 
 	// from android package