Add 'soong_config_variable' selection

src/grammar.json

@@ -253,8 +253,17 @@
           "value": "("
         },
         {
-          "type": "SYMBOL",
-          "name": "select_value"
+          "type": "CHOICE",
+          "members": [
+            {
+              "type": "SYMBOL",
+              "name": "select_value"
+            },
+            {
+              "type": "SYMBOL",
+              "name": "soong_config_variable"
+            }
+          ]
         },
         {
           "type": "STRING",
@@ -317,6 +326,61 @@
         }
       ]
     },
+    "soong_config_variable": {
+      "type": "SEQ",
+      "members": [
+        {
+          "type": "FIELD",
+          "name": "type",
+          "content": {
+            "type": "ALIAS",
+            "content": {
+              "type": "STRING",
+              "value": "soong_config_variable"
+            },
+            "named": true,
+            "value": "selection_type"
+          }
+        },
+        {
+          "type": "STRING",
+          "value": "("
+        },
+        {
+          "type": "FIELD",
+          "name": "condition",
+          "content": {
+            "type": "SEQ",
+            "members": [
+              {
+                "type": "FIELD",
+                "name": "namespace",
+                "content": {
+                  "type": "SYMBOL",
+                  "name": "_string_literal"
+                }
+              },
+              {
+                "type": "STRING",
+                "value": ","
+              },
+              {
+                "type": "FIELD",
+                "name": "variable",
+                "content": {
+                  "type": "SYMBOL",
+                  "name": "_string_literal"
+                }
+              }
+            ]
+          }
+        },
+        {
+          "type": "STRING",
+          "value": ")"
+        }
+      ]
+    },
     "select_cases": {
       "type": "SEQ",
       "members": [

src/node-types.json

@@ -348,6 +348,10 @@
         {
           "type": "select_value",
           "named": true
+        },
+        {
+          "type": "soong_config_variable",
+          "named": true
         }
       ]
     }
@@ -382,6 +386,60 @@
       }
     }
   },
+  {
+    "type": "soong_config_variable",
+    "named": true,
+    "fields": {
+      "condition": {
+        "multiple": false,
+        "required": true,
+        "types": [
+          {
+            "type": ",",
+            "named": false
+          }
+        ]
+      },
+      "namespace": {
+        "multiple": false,
+        "required": true,
+        "types": [
+          {
+            "type": "interpreted_string_literal",
+            "named": true
+          },
+          {
+            "type": "raw_string_literal",
+            "named": true
+          }
+        ]
+      },
+      "type": {
+        "multiple": false,
+        "required": true,
+        "types": [
+          {
+            "type": "selection_type",
+            "named": true
+          }
+        ]
+      },
+      "variable": {
+        "multiple": false,
+        "required": true,
+        "types": [
+          {
+            "type": "interpreted_string_literal",
+            "named": true
+          },
+          {
+            "type": "raw_string_literal",
+            "named": true
+          }
+        ]
+      }
+    }
+  },
   {
     "type": "source_file",
     "named": true,