Protect line endings in shell scripts

Add a .gitattributes file to prevent /bin/sh scripts from
getting clobbered by git config core.autocrlf=true setting.

Change-Id: I3dfc992a9c275fceae64c9719168d81e60d911bd

.gitattributes

@@ -0,0 +1,4 @@
+# Prevent /bin/sh scripts from being clobbered by autocrlf=true
+git_ssh text eol=lf
+main.py text eol=lf
+repo text eol=lf