Meta: Add CodeGenerators and library dependencies for them to gn build

Meta/gn/secondary/Userland/Libraries/LibFileSystem/BUILD.gn

@@ -0,0 +1,14 @@
+shared_library("LibFileSystem") {
+  include_dirs = [ "//Userland/Libraries" ]
+  sources = [
+    "FileSystem.cpp",
+    "FileSystem.h",
+    "TempFile.cpp",
+    "TempFile.h",
+  ]
+  deps = [
+    "//AK",
+    "//Userland/Libraries/LibCore",
+  ]
+  output_name = "filesystem"
+}

Meta/gn/secondary/Userland/Libraries/LibIPC/BUILD.gn

@@ -0,0 +1,26 @@
+shared_library("LibIPC") {
+  output_name = "ipc"
+  include_dirs = [ "//Userland/Libraries" ]
+  sources = [
+    "Concepts.h",
+    "Connection.cpp",
+    "Connection.h",
+    "ConnectionFromClient.h",
+    "ConnectionToServer.h",
+    "Decoder.cpp",
+    "Decoder.h",
+    "Dictionary.h",
+    "Encoder.cpp",
+    "Encoder.h",
+    "File.h",
+    "Forward.h",
+    "Message.h",
+    "MultiServer.h",
+    "SingleServer.h",
+    "Stub.h",
+  ]
+  deps = [
+    "//AK",
+    "//Userland/Libraries/LibCore",
+  ]
+}

Meta/gn/secondary/Userland/Libraries/LibMain/BUILD.gn

@@ -0,0 +1,9 @@
+static_library("LibMain") {
+  include_dirs = [ "//Userland/Libraries" ]
+  sources = [
+    "Main.cpp",
+    "Main.h",
+  ]
+  deps = [ "//AK" ]
+  output_name = "main"
+}

Meta/gn/secondary/Userland/Libraries/LibTimeZone/BUILD.gn

@@ -0,0 +1,22 @@
+declare_args() {
+  # If true, Download tzdata from data.iana.org and use it in LibTimeZone
+  # Data will be downloaded to $cache_path/TZDB
+  enable_timezone_database_download = false
+}
+
+source_set("LibTimeZone") {
+  output_name = "timezone"
+  include_dirs = [ "//Userland/Libraries" ]
+  sources = [
+    "Forward.h",
+    "TimeZone.cpp",
+    "TimeZone.h",
+  ]
+  deps = [
+    "//AK",
+    "//Userland/Libraries/LibCore",
+  ]
+  if (enable_timezone_database_download) {
+    deps += [ ":timezone_data" ]
+  }
+}