Cmake doesn't see variable from find_path - c++

Question

I am trying to compile code with activemq-cpp with cmake and gcc 5.4
find_path(ACTIVEMQCPP_DIR NAMES cms/Config.h HINTS $ENV{ACTIVEMQDIR})
Here ACTIVEMQDIR is an environment variable set to
/usr/local/include/activemq-cpp-3.10.0
message(STATUS ACTIVEMQCPP_DIR=${ACTIVEMQCPP_DIR})
include_directories(${ACTIVEMQCPP_DIR})
//include_directories(/usr/local/include/activemq-cpp-3.10.0)
If i hardcode path explicitly, then it is ok...
Output from cmake:
-- The C compiler identification is GNU 5.4.0
-- The CXX compiler identification is GNU 5.4.0
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- 1=/usr/local/include/activemq-cpp-3.10.0
-- 2=/usr/local/lib
-- 3=/usr/local/include/activemq-cpp-3.10.0
-- 4=/usr/local/lib/libactivemq-cpp.so
-- Configuring done
-- Generating done
-- Build files have been written to
-- The C compiler identification is GNU 5.4.0
-- The CXX compiler identification is GNU 5.4.0
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
ACTIVEMQCPP_DIR=/usr/local/include/activemq-cpp-3.10.0
-- Configuring done
-- Generating done
-- Build files have been written to: /home/oem/ClionProjects/untitled/b2
The problem is that include_directories(${ACTIVEMQCPP_DIR}) doesn't work. Variable ACTIVEMQCPP_DIR is not set

Answer 1

Write it like this
include_directories($ENV{ACTIVEMQCPP_DIR})
so that cmake knows it's an environemnt variable.