build: unset GOROOT_FINAL before tests

        Fix the builders.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5976068

src/run.bash

@@ -24,6 +24,11 @@ else
 	echo
 fi
 
+# we must unset GOROOT_FINAL before tests, because runtime/debug requires
+# correct access to source code, so if we have GOROOT_FINAL in effect,
+# at least runtime/debug test will fail.
+unset GOROOT_FINAL
+
 echo '# Testing packages.'
 time go test std -short -timeout=120s
 echo

src/run.bat

@@ -25,6 +25,11 @@ if errorlevel 1 goto fail
 echo.
 :norebuild
 
+:: we must unset GOROOT_FINAL before tests, because runtime/debug requires
+:: correct access to source code, so if we have GOROOT_FINAL in effect,
+:: at least runtime/debug test will fail.
+set GOROOT_FINAL=
+
 echo # Testing packages.
 go test std -short -timeout=120s
 if errorlevel 1 goto fail