Add arm_neon.h and remove CMakeLists.txt

This commit copies `arm_neon.h` from `prebuilts/clang/host` and removes
unused `CMakeLists.txt`.

Bug: 111579848
Test: ./prebuilts/clang-tools/build-prebuilts.sh  # (on aosp/clang-tools
branch)

Change-Id: I7398cfc8f5399ea8b3fc838a41d8e294e71bc598
1 file changed
tree: e687fadcf7cac0b627ecac57ff9c18952a6afe6b
  1. darwin-x86/
  2. linux-x86/
  3. build-prebuilts.sh
  4. manifest.xml