Add host_supported to libskia_skcms

Necessary for some fuzzer dependencies. libskia is
already marked host_supported: true as well, so this isn't
a meaningful incremental support requirement

Change-Id: If70eb354bc0818eacd9fffe9dc8d792e89b1b7b1
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/1004922
Reviewed-by: Daniel Dilan <danieldilan@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
Reviewed-by: Ben Wagner <bungeman@google.com>