Revert "[gn] Extract target_os, target_cpu resolution (#33224)" (#33231)
Revert "[gn] Extract target_os, target_cpu resolution (#33224)" (#33231)

This reverts commit 9cb49937575fa9b6774e9dc471ce638e151ccf47.
devoncarew/engine,chinmaygarde/flutter_engine,devoncarew/engine,chinmaygarde/flutter_engine,flutter/engine,rmacnak-google/engine,flutter/engine,rmacnak-google/engine,chinmaygarde/flutter_engine,chinmaygarde/flutter_engine,flutter/engine,devoncarew/engine,chinmaygarde/flutter_engine,devoncarew/engine,flutter/engine,rmacnak-google/engine,rmacnak-google/engine,chinmaygarde/flutter_engine,flutter/engine,rmacnak-google/engine,rmacnak-google/engine,devoncarew/engine,chinmaygarde/flutter_engine,flutter/engine,devoncarew/engine,flutter/engine,rmacnak-google/engine,flutter/engine,devoncarew/engine