Error in building example

[xingxu21]

Upon running cmake .. I received the following issue:

`-- The C compiler identification is GNU 5.4.0
-- The CXX compiler identification is unknown
-- 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
CMake Error at CMakeLists.txt:2 (project):
No CMAKE_CXX_COMPILER could be found.

Tell CMake where to find the compiler by setting either the environment
variable "CXX" or the CMake cache entry CMAKE_CXX_COMPILER to the full path
to the compiler, or to the compiler name if it is in the PATH.

-- Configuring incomplete, errors occurred!
See also "/home/xingxu/cpr-example/build/CMakeFiles/CMakeOutput.log".
See also "/home/xingxu/cpr-example/build/CMakeFiles/CMakeError.log".`

I'm running this under linux.