Initial libcore fuchsia support.

This CL is a squash of the following internal commits,
save changes to libcore_io_Linux.cpp and NativeCode.bp
which require further consideration and a dependency on
Soong changes.

    9d2d1b7f21
    89f57aea27
    23243ec41f
    72f0ec6baf
    d9aa13b5a5

Bug: 119271070
Bug: 119504167
Test: Compile walleye. Note that no fuchsia target
exists yet on aosp.
Change-Id: Ib89c8e55b4a2a50df86d690fab537c45afcc93a4
9 files changed