Linux packager: Make sure ELF binaries live exclusively in /opt

BUG=768020
R=thestig@chromium.org

Change-Id: Iaf520e6f064cdc44977607fdac8be7137648bbfd
Reviewed-on: https://chromium-review.googlesource.com/685506Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#504460}

chrome/installer/linux/common/installer.include

@@ -295,6 +295,16 @@ stage_install_common() {
     exit 1
   fi
 
+  # Make sure ELF binaries live in INSTALLDIR exclusively.
+  ELF_OUTSIDE_INSTALLDIR=$(find "${STAGEDIR}/" -not -path \
+    "${STAGEDIR}${INSTALLDIR}/*" -type f | xargs file -b |
+    grep -ce "^ELF" || true)
+  if [ "${ELF_OUTSIDE_INSTALLDIR}" -ne 0 ]; then
+    echo "ERROR: Found ${ELF_OUTSIDE_INSTALLDIR} ELF binaries" \
+      "outside of ${INSTALLDIR}" 1>&2
+    exit 1
+  fi
+
   # Verify file permissions.
   for file in $(find "${STAGEDIR}" -mindepth 1); do
     local actual_perms=$(stat -c "%a" "${file}")