Fix exec bits in build/scripts

This turn on the executable bit for scripts that have a shebang.
dcommitting b/c CQ can't process file mode changes

(hasher.py has a shebang but shouldn't; will commit separately
so only dcommit file mode changes.)

TBR=abarth

Review URL: https://codereview.chromium.org/238833002

git-svn-id: svn://svn.chromium.org/blink/trunk@171547 bbb929c8-8fbe-4397-9dbb-9b2b20218538