chrome/installer: Fix the cros chrome-sdk build.

The target chrome/installer/linux:calculate_deb_dependencies is broken
in the cros chrome-sdk shell build because is_linux is true in addition
to is_chromeos.

This change prevents the linux installer from being enabled when
is_chromeos is true.

R=gab@chromium.org

Bug: 867013
Test: none
Change-Id: I1596177528c35a4670fad52e62d56ad0ba104a16
Reviewed-on: https://chromium-review.googlesource.com/1150443
Reviewed-by: Gabriel Charette <gab@chromium.org>
Commit-Queue: James Hawkins <jhawkins@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578336}
diff --git a/chrome/installer/BUILD.gn b/chrome/installer/BUILD.gn
index e058d04..0c6167c 100644
--- a/chrome/installer/BUILD.gn
+++ b/chrome/installer/BUILD.gn
@@ -8,7 +8,8 @@
 
 declare_args() {
   enable_linux_installer =
-      is_linux && !is_component_build && use_sysroot && !using_sanitizer
+      is_linux && !is_chromeos && !is_component_build && use_sysroot &&
+      !using_sanitizer
 }
 
 # Meta-target that forwards to the installer of the correct type (if any).