[C++] ARROW_ORC=ON breaks: fatal error: 'orc/OrcFile.hh' file not found

```java

FAILED: src/arrow/CMakeFiles/arrow_objlib.dir/adapters/orc/adapter_util.cc.o
/usr/bin/c++ -DARROW_WITH_LZ4 -DARROW_WITH_SNAPPY -DARROW_WITH_TIMING_TESTS -DARROW_WITH_ZLIB -DARROW_WITH_ZSTD -DURI_STATIC_BUILD -Isrc -I/disk-samsung/freebsd-ports/databases/arrow/work/apache-arrow-4.0.0/cpp/src -I/disk-samsung/freebsd-ports/databases/arrow/work/apache-arrow-4.0.0/cpp/src/generated -isystem /disk-samsung/freebsd-ports/databases/arrow/work/apache-arrow-4.0.0/cpp/thirdparty/flatbuffers/include -isystem /disk-samsung/freebsd-ports/databases/arrow/work/apache-arrow-4.0.0/cpp/thirdparty/hadoop/include -isystem orc_ep-install/include -O2 -pipe -fno-omit-frame-pointer -fstack-protector-strong -isystem /usr/local/include -fno-strict-aliasing -fno-omit-frame-pointer -isystem /usr/local/include -Qunused-arguments -fcolor-diagnostics -O3 -DNDEBUG -Wall -Wno-unknown-warning-option -Wno-pass-failed -O2 -pipe -fno-omit-frame-pointer -fstack-protector-strong -isystem /usr/local/include -fno-strict-aliasing -fno-omit-frame-pointer -isystem /usr/local/include -fPIC -std=c++11 -MD -MT src/arrow/CMakeFiles/arrow_objlib.dir/adapters/orc/adapter_util.cc.o -MF src/arrow/CMakeFiles/arrow_objlib.dir/adapters/orc/adapter_util.cc.o.d -o src/arrow/CMakeFiles/arrow_objlib.dir/adapters/orc/adapter_util.cc.o -c /disk-samsung/freebsd-ports/databases/arrow/work/apache-arrow-4.0.0/cpp/src/arrow/adapters/orc/adapter_util.cc
In file included from /disk-samsung/freebsd-ports/databases/arrow/work/apache-arrow-4.0.0/cpp/src/arrow/adapters/orc/adapter_util.cc:18:
/disk-samsung/freebsd-ports/databases/arrow/work/apache-arrow-4.0.0/cpp/src/arrow/adapters/orc/adapter_util.h:25:10: fatal error: 'orc/OrcFile.hh' file not found
#include "orc/OrcFile.hh"
^~~~~~~~~~~~~~~~
1 error generated.

```
This file is present:
```java

$ find . -name OrcFile.hh
./work/stage/disk-samsung/freebsd-ports/databases/arrow/work/.build/orc_ep-install/include/orc/OrcFile.hh
./work/.build/orc_ep-prefix/src/orc_ep/c++/include/orc/OrcFile.hh
```
but the build fails to find it.

The build is outsource.

**Environment**: OS: FreeBSD 12.2

**Reporter**: [Yuri](https://issues.apache.org/jira/browse/ARROW-12624) / @yurivict

_{**Note**: *This issue was originally created as [ARROW-12624](https://issues.apache.org/jira/browse/ARROW-12624). Please see the [migration documentation](https://github.com/apache/arrow/issues/14542) for further details.*}

Start by reproducing the FreeBSD 12.2 build with ARROW_ORC=ON and inspect the include paths used while compiling src/arrow/adapters/orc/adapter_util.cc and adapter_util.h. Compare the generated orc_ep-install/include path with the path passed to the compiler; done means the ORC-enabled C++ build finds orc/OrcFile.hh and completes successfully.

Written by the indexing model from the issue text.