[opt-viewer] Check for pygments.lexer.c_cpp

[Hahnfeld]

Summary

Some systems still don't have module which was introduced in
version 2.0 (CentOS 7, sigh).

[anemet]

LGTM. Thanks!

cmake/config-ix.cmake

else()
       endif()
     endif()
   endif()
 endif()
 
 string(REPLACE " " ";" LLVM_BINDINGS_LIST "${LLVM_BINDINGS}")
 
 function(find_python_module module)
-  string(TOUPPER ${module} module_upper)
+  string(REPLACE "." "_" module_name ${module})
+  string(TOUPPER ${module_name} module_upper)
   set(FOUND_VAR PY_${module_upper}_FOUND)
 
   execute_process(COMMAND "${PYTHON_EXECUTABLE}" "-c" "import ${module}"
     RESULT_VARIABLE status
     ERROR_QUIET)
 
   if(status)
     set(${FOUND_VAR} 0 PARENT_SCOPE)
     message(STATUS "Could NOT find Python module ${module}")
   else()
     set(${FOUND_VAR} 1 PARENT_SCOPE)
     message(STATUS "Found Python module ${module}")
   endif()
 endfunction()
 
 set (PYTHON_MODULES
   pygments
+  # Some systems still don't have pygments.lexers.c_cpp which was introduced in
+  # version 2.0 in 2014...
+  pygments.lexers.c_cpp
   yaml
   )
 foreach(module ${PYTHON_MODULES})
   find_python_module(${module})
 endforeach()
 
-if(PY_PYGMENTS_FOUND AND PY_YAML_FOUND)
+if(PY_PYGMENTS_FOUND AND PY_PYGMENTS_LEXERS_C_CPP_FOUND AND PY_YAML_FOUND)
   set (LLVM_HAVE_OPT_VIEWER_MODULES 1)
 else()
   set (LLVM_HAVE_OPT_VIEWER_MODULES 0)
 endif()