Install arm_compute_XXX and libnueralnetworks.so on pure_arm_compute … (#1393)

Install arm_compute_XXX and libnueralnetworks.so on pure_arm_compute … (#1393)

* Install arm_compute_XXX and libnueralnetworks.so on pure_arm_compute build

1. On pure_arm_compute runtime build, install arm_compute_XXX.so into lib
2. DO NOT build NN Runtime if BUILD_ACL=ON

Signed-off-by: Chunseok Lee <chunseok.lee@samsung.com>
* Add option BUILD_PURE_ARM_COMPUTE and change install dir

Signed-off-by: Chunseok Lee <chunseok.lee@samsung.com>
* Remove `BUILD_NN_RUNTIME` option off

Since pure_acl_compute runtime is installed to lib/pureacl, we do not need turn
off option BUILD_NN_RUNTIME.

Signed-off-by: Chunseok Lee <chunseok.lee@samsung.com>
* Apply suggestion

In summary,
1. install arm_compute_xxx to lib
2. install libnn.so to lib/pureacl

Signed-off-by: Chunseok Lee <chunseok.lee@samsung.com>