do not build systray in linux

src/systray/NOTES.txt

@@ -9,3 +9,4 @@ hash:
 changes:
 
 -removed `getlantern/golog` dependency
+-prevent from compiling in linux

src/systray/systray.go

@@ -1,3 +1,5 @@
+// +build darwin,windows
+
 /*
 Package systray is a cross-platform Go library to place an icon and menu in the notification area.
 */

src/systray/systray_linux.go

@@ -1,3 +1,5 @@
+// +build never
+
 package systray
 
 /*

src/systray/systray_nonwindows.go

@@ -1,9 +1,8 @@
-// +build !windows
+// +build darwin
 
 package systray
 
 /*
-#cgo linux pkg-config: gtk+-3.0 appindicator3-0.1
 #cgo darwin CFLAGS: -DDARWIN -x objective-c -fobjc-arc
 #cgo darwin LDFLAGS: -framework Cocoa