Automake includes full support for C++.
Any package including C++ code must define the output variable
CXX in configure.ac; the simplest way to do this is to use
the AC_PROG_CXX macro (see Particular Program Checks).
A few additional variables are defined when a C++ source file is seen:
CXXCXXFLAGSAM_CXXFLAGSCXXFLAGS.
CXXCOMPILECXXLINK