fix broken build flag, move build to one directory

[sam-herman]

Description

Addresses a bug and house cleaning during build.

1. Cmake has invalid syntax in if condition causing this message:

CMake Error at cmake/init-faiss.cmake:114 (if):
  if given arguments:

    "AND" "NOT" "" "STREQUAL" ""

  Unknown arguments specified
Call Stack (most recent call first):
  CMakeLists.txt:107 (include)

2. Move all build artifacts created into a build directory following conventional build standards. Currently there are multiple temporary artifacts generated by cmake which are scattered under jni directory.

Related Issues

Resolves #[Issue number to be closed when this PR is merged]

Check List

• [ x] New functionality includes testing.
• [x ] New functionality has been documented.
• [x ] API changes companion pull request created.
• [ x] Commits are signed per the DCO using --signoff.
• [ x] Public documentation issue/PR created.

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