Add WASM os target to public.bzl
Add WASM os target to public.bzl

prerequisite to cl/297131877

Bug: b/150386856
Change-Id: I23a770c59ca7c2899ef5e045194a1bf9c27d9449
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/274048
Commit-Queue: Nathaniel Nifong <1ce561679465ea4956c6210637580cd7ba456816@google.com>
Reviewed-by: Kevin Lubick <7cdab2cfab351f23814786ba39716e90eed69047@google.com>

aosp-mirror/platform_external_skia,google/skia,google/skia,google/skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,google/skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia