Enable strip in newlib_pnacl_nonsfi toolchain

Now that the PNaCl toolchain has been updated so that pnacl-strip
accepts the --strip-unneeded switch, the nacl-nonsfi builds can use it.

BUG= none
R=dpranke@chromium.org

Review URL: https://codereview.chromium.org/1474833002

Cr-Original-Commit-Position: refs/heads/master@{#361455}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 856e261366bc19b437fec95d478fbc3c679e07db

toolchain/nacl/BUILD.gn

@@ -71,9 +71,7 @@ pnacl_toolchain("newlib_pnacl") {
 
 pnacl_toolchain("newlib_pnacl_nonsfi") {
   executable_extension = ""
-  # TODO(mcgrathr): Uncomment this after pnacl-strip has been taught
-  # to grok --strip-unneeded.
-  #strip = "strip"
+  strip = "strip"
 }
 
 template("nacl_glibc_toolchain") {