default installation folder shoulbe be /usr/local, not /usr

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### Expected behavior

by default user compiles/installed packages should land on /usr/local/ not /usr/

### Actual behavior

installation files land on /usr/* instead of /usr/local

### Steps to reproduce the behavior

```bash
mkdir _build
cd _build
cmake ..
make
sudo make install
ls -al /usr/local/include/rocksdb # -> error
ls -al /usr/include/rocksdb # -> files are here
```