configure script should check for a C++ compiler before checking for FlexLexer.h
While setting up a Kubuntu 23.04 VM, I noticed that even though Flex was installed, the configure
script kept complaining
ERROR: Please install required programs: FlexLexer.h (flex package) FlexLexer.h with yypop_buffer_state (flex >= 2.5.29)
Reading config.log
showed that the missing element was in fact g++
.