make shellcheck (linter) recommended changes to bin/flutter (#30456)
make shellcheck (linter) recommended changes to bin/flutter (#30456)


cbracken/flutter,tvolkert/flutter,tvolkert/flutter,Hixie/flutter,cbracken/flutter,cbracken/flutter,flutter/flutter,tvolkert/flutter,tvolkert/flutter,flutter/flutter,tvolkert/flutter,flutter/flutter,cbracken/flutter,flutter/flutter,cbracken/flutter,cbracken/flutter,Hixie/flutter,tvolkert/flutter,Hixie/flutter,cbracken/flutter,Hixie/flutter,flutter/flutter,tvolkert/flutter,Hixie/flutter,tvolkert/flutter,tvolkert/flutter,flutter/flutter,flutter/flutter,Hixie/flutter,tvolkert/flutter,cbracken/flutter,flutter/flutter,cbracken/flutter,Hixie/flutter,cbracken/flutter,flutter/flutter,Hixie/flutter,Hixie/flutter,flutter/flutter,Hixie/flutter