[emulator] Produce 64-Bit darwin & linux binaries.

- We now target x64 vs i386 since we no longer support i386.
  This fixes some issues users are seeing around 32-bit binaries.

Change-Id: I7b71107b792b2f04eeebd8cdd2230885931a9578
Bug: b/37132646
Test: file mksdcard => mksdcard: ELF 64-bit LSB  executable, x86-64, version 1 (SYSV)
Test: file mksdcard => mksdcard: Mach-O 64-bit executable x86_64
1 file changed
tree: 1d643ae8ca8c7808e93864047e0674d666112a36
  1. .gitignore
  2. README
  3. base/
  4. build.gradle
  5. readme.txt
  6. servers/
  7. src/