CLI is always reinstalled by init-tools.sh

[dagood]

This is making the CLI always install on my Fedora 26 runs (and probably other shells):

source-build/init-tools.sh

Lines 17 to 20 in 51f2c9a

	if [ -e $__BUILD_TOOLS_SEMAPHORE ]; then
	echo "Tools are already initialized"
	return #return instead of exit because this script is inlined in other scripts which we don't want to exit
	fi

/home/dagood/git/here-source-build/init-tools.sh: line 19: return: can only `return' from a function or sourced script

Two fixes come to mind:

1. Wrap the rest of the file with else rather than trying to early return.
2. Put the code in a function and keep using return.

@weshaggard @eerhardt

[weshaggard]

Most repo's are sourcing in the init-tools script which is why we needed it to be a return instead of exit. That said I was under the impression that return should turn into an exit if it is an outer script, perhaps my understand is incorrect on that front.

I will do some testing but if this is blocking you the easiest fix is to source in the script from build.sh.

[dagood]

Looking at the PR that changed from executing to sourcing (dotnet/corefx#19363), switching to sourcing is actually better anyway. The only remaining problem is anyone calling ./init-tools.sh, but I don't have a reason to support that.