python3 for building ninja (#5673)

Author: mununki

scripts/buildNinjaBinary.js

@@ -6,7 +6,7 @@ const path = require("path");
 
 const platform = process.platform;
 const ninjaDir = path.join(__dirname, "..", "ninja");
-const buildCommand = "python configure.py --bootstrap --verbose";
+const buildCommand = "python3 configure.py --bootstrap --verbose";
 
 if (platform === "win32") {
   // On Windows, the build uses the MSVC compiler which needs to be on the path.