Support building diagnose_usb against musl by reimplementing
group_member, which doesn't exist in musl and isn't used anywhere
else in the tree.
Bug: 190084016
Test: m USE_HOST_MUSL=true host-native
Change-Id: Id0fe51d0bd8677561d0bbdb72d3b1a956127a11c
Rearrange some files while we're doing this.
Bug: http://b/71721338
Test: manually ran adb on windows
Change-Id: Ie47bda82279e4b9521505ad0353bf9ef649fc7d7