jiri: fix typo and add example for "jiri test run -pkgs"

Change-Id: Id370d070cf189a0f08e496a79d58f090e3089e26
MultiPart: 1/2
diff --git a/profiles/target.go b/profiles/target.go
index 2ff4b59..76ba920 100644
--- a/profiles/target.go
+++ b/profiles/target.go
@@ -286,7 +286,7 @@
 
 // Usage returns the usage string for Environment.
 func (e *Environment) Usage() string {
-	return "specifcy an environment variable in the form: <var>=[<val>],..."
+	return "specify an environment variable in the form: <var>=[<val>],..."
 }
 
 // InsertTarget inserts the given target into Targets if it's not