Move linux channel mapping logic to //brave/build/config.gni

BUILD.gn

@@ -74,15 +74,8 @@ group("create_dist") {
     deps += [ "build/mac:create_dist_mac" ]
   }
   if (is_linux) {
-    _linux_channel = brave_channel
-    if (brave_channel == "") {
-      _linux_channel = "stable"
-    } else if (brave_channel == "dev") {
-      _linux_channel = "unstable"
-    }
-
     deps += [
-      "//chrome/installer/linux:$_linux_channel",
+      "//chrome/installer/linux:$brave_linux_channel",
       "//brave/app/linux:dist_resources",
     ]
   }

build/config.gni

@@ -25,6 +25,18 @@ if (is_win) {
   brave_exe = "$chrome_product_full_name.app"
 }
 
+if (is_linux) {
+  # Our channle name and upstream linux channel name is different.
+  brave_linux_channel = ""
+  if (brave_channel == "") {
+    brave_linux_channel = "stable"
+  } else if (brave_channel == "dev") {
+    brave_linux_channel = "unstable"
+  } else {
+    assert(brave_channel == "beta", "Not supported channel name: $brave_channel")
+  }
+}
+
 brave_icon_dir = "nightly"
 if (is_component_build) {
   brave_icon_dir = "dev"