[gn build] Port a1b14db

Author: llvmgnsyncbot

llvm/utils/gn/secondary/lldb/source/Host/BUILD.gn

@@ -17,7 +17,6 @@ static_library("Host") {
   public_deps = [ "//llvm/utils/gn/build/libs/xml" ]
   sources = [
     "aix/HostInfoAIX.cpp",
-    "common/Alarm.cpp",
     "common/File.cpp",
     "common/FileAction.cpp",
     "common/FileCache.cpp",