configure fails to detect if C++ compiler is present

[giulianobelinassi]

When running make check, the configure script fails to verify if the C++ compiler is indeed working:

libtool: compile:  g++ -DHAVE_CONFIG_H -I. -I../../libpulp/tests -I../include -fPIC -fpatchable-function-entry=24,22 -fno-inline -Wall -Wextra -Werror -c ../../libpulp/tests/libexception.cc  -o .libs/libexception_la-libexception.o
../libtool: line 1762: g++: command not found

This should have failed during configure.