Okay, so here's what happens when you type a verse from memory that you never really quite learned right, and haven't performed in several months: you type something different.
This, my friends, is what they call the "folk process."
So, what it really has in "Rise Up Singing" for that verse is:
I will build my love a shelter
By yon high mountain green
And my love shall be the fairest
That the summer sun has seen
"Shelter" for some reason feels too prosaic there--maybe that's why I remembered it differently.
And Mbo, I do see what you mean. That scansion has never really bothered me, but you gotta sing things in a way that feels comfortable for you.