Migrate libchromeos to its own ebuild

All platform2 packages should have their own ebuild that will be compiled
independently. Packages should DEPEND on libchromeos and should not have a gyp
dependency on libchromeos's gyp file anymore.

BUG=chromium:381372
TEST=emerge-daisy libchromeos && emerge-daisy platform2 work
TEST=trybot run on daisy, link, mario and duck.
TEST=trybot run on lumpy-incremental-paladin.

CQ-DEPEND=CL:202748

Change-Id: Ic34f8ae1c8ef1295c33d7a767f18f9d25c4e3480
Reviewed-on: https://chromium-review.googlesource.com/202770
Tested-by: Bertrand Simonnet <[email protected]>
Reviewed-by: Mike Frysinger <[email protected]>
Commit-Queue: Bertrand Simonnet <[email protected]>
diff --git a/cros-disks.gyp b/cros-disks.gyp
index 85859a9..d7ec212 100644
--- a/cros-disks.gyp
+++ b/cros-disks.gyp
@@ -1,7 +1,6 @@
 {
   'target_defaults': {
     'dependencies': [
-      '../../platform2/libchromeos/libchromeos-<(libbase_ver).gyp:libchromeos-<(libbase_ver)',
       '../metrics/libmetrics-<(libbase_ver).gyp:libmetrics-<(libbase_ver)',
     ],
     'libraries': [
@@ -16,6 +15,7 @@
         'gobject-2.0',
         'gthread-2.0',
         'libchrome-<(libbase_ver)',
+        'libchromeos-<(libbase_ver)',
         'libudev',
       ],
     },
@@ -40,7 +40,10 @@
     {
       'target_name': 'libdisks',
       'type': 'static_library',
-      'dependencies': ['libdisks-adaptors'],
+      'dependencies': [
+        '<(platform_root)/system_api/system_api.gyp:system_api-headers',
+        'libdisks-adaptors',
+      ],
       'sources': [
         'archive_manager.cc',
         'cros_disks_server.cc',