Fix chapter 4 for PGI testing

Author: robertodr

chapter-04/recipe-04/cxx-example/menu.yml

@@ -3,6 +3,11 @@ appveyor-vs:
     - BOOST_ROOT: 'C:\Libraries\boost_1_67_0'
     - CMAKE_CXX_FLAGS: '-DBOOST_ALL_NO_LIB'  
 
+circle-pgi:
+  definitions:
+   - BOOST_INCLUDEDIR: '/usr/include/boost'
+   - BOOST_LIBRARYDIR: '/usr/lib/x86_64-linux-gnu'
+
 travis-osx:
   definitions:
     - BOOST_ROOT: '/usr/local/opt/boost@1.59'