soong: add os name to cc_genrule

While converting from gn to bp we stumbled upon genrules that have different cmd's for different targets. cc_genrule supports different architectures, but it does not give us any information about the OS types (some genrules are use for both host and android targets).

Change-Id: Ida531ad8b59d87a91d6faedbfe8fee9f75640bd1
Test: TH