Add installer_util_unittests to the GN windows build
This fixes some C++ Warnings on Windows to avoid having to add suppressions to the GN build.
Moves the generated strings header to the same place in the gen tree as it is in the source tree. Update includes.
CQ_EXTRA_TRYBOTS=tryserver.chromium.linux:android_chromium_gn_compile_dbg,android_chromium_gn_compile_rel;tryserver.chromium.win:win8_chromium_gn_rel,win8_chromium_gn_dbg;tryserver.chromium.mac:mac_chromium_gn_rel,mac_chromium_gn_dbg
Review URL: https://codereview.chromium.org/
1062743006
Cr-Commit-Position: refs/heads/master@{#327790}