Cherry-pick local changes to 9.2

Cherry-picked commits:
    b711aa8: Add Unix domain socket support to gdbserver 7.9.1.
    4c58332: Go back to snprintf rather than strlcpy.
    c64829b: Fallback to open if multifs_open fails.
    2177073: Fix gdbserver process interruption.
    35ee683: Remove gdb hack.
    78af0f6: Handle cross compile for locale configuration
    dfc5ca4: Set the default gdb osabi to GNU/Linux.
    5cbd102: Specify osabi in arm/aarch64 tdescs. (updated)
    d378e66: Explicit link -ldl for gdbserver

Test: build
Change-Id: Iea7f0159ad5d4f5edba0db215a96bc85b3f332cd
10 files changed
tree: 3b8e919bc09f84590e2c43d8dd77d6d7979c3d4d
  1. gdb-8.3/
  2. gdb-9.1/
  3. gdb-9.2/