test: adapt old-style tests to new flag parsing.

The -I. syntax now needs a space to be recognized in the
compiler.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/7098046

test/safe/nousesafe.go

-// $G $D/pkg.go && pack grc pkg.a pkg.$A 2> /dev/null && rm pkg.$A && errchk $G -I. -u $D/main.go
+// $G $D/pkg.go && pack grc pkg.a pkg.$A 2> /dev/null && rm pkg.$A && errchk $G -I . -u $D/main.go
 // rm -f pkg.a
 
 // Copyright 2012 The Go Authors. All rights reserved.

test/safe/usesafe.go

-// $G $D/pkg.go && pack grcS pkg.a pkg.$A 2> /dev/null && rm pkg.$A && $G -I. -u $D/main.go
+// $G $D/pkg.go && pack grcS pkg.a pkg.$A 2> /dev/null && rm pkg.$A && $G -I . -u $D/main.go
 // rm -f pkg.a
 
 // Copyright 2012 The Go Authors. All rights reserved.