Problema e soluzione installazione squidGuard su fedora e CentOS - lex.yy.c

Nel caso in cui, durante l'installazione di squidguard si riceve il
seguente errore:

[root@proxy squidGuard-1.3]# make
making all in squidGuard-1.3
make[1]: Entering directory `/root/sw/squidGuard-1.3/src'
making all in src
gcc -I.. -I. -I. -I/usr/local/BerkeleyDB/include -DHAVE_CONFIG_H -g -O2
-I/usr/local/BerkeleyDB/include -c main.c
gcc -I.. -I. -I. -I/usr/local/BerkeleyDB/include -DHAVE_CONFIG_H -g -O2
-I/usr/local/BerkeleyDB/include -c sgLog.c
gcc -I.. -I. -I. -I/usr/local/BerkeleyDB/include -DHAVE_CONFIG_H -g -O2
-I/usr/local/BerkeleyDB/include -c sgDb.c
gcc -I.. -I. -I. -I/usr/local/BerkeleyDB/include -DHAVE_CONFIG_H -g -O2
-I/usr/local/BerkeleyDB/include -c sgDiv.c
gcc -I.. -I. -I. -I/usr/local/BerkeleyDB/include -DHAVE_CONFIG_H -g -O2
-I/usr/local/BerkeleyDB/include -c sgFree.c
yacc -d sg.y || (cp y.tab.c.bison y.tab.c && cp y.tab.h.bison y.tab.h)
/bin/sh: yacc: command not found
gcc -I.. -I. -I. -I/usr/local/BerkeleyDB/include -DHAVE_CONFIG_H -g -O2
-I/usr/local/BerkeleyDB/include -c y.tab.c
: sg.l || cp lex.yy.c.flex lex.yy.c
gcc -I.. -I. -I. -I/usr/local/BerkeleyDB/include -DHAVE_CONFIG_H -g -O2
-I/usr/local/BerkeleyDB/include -c lex.yy.c
gcc: lex.yy.c: No such file or directory
gcc: no input files
make[1]: *** [lex.yy.o] Error 1
make[1]: Leaving directory `/root/sw/squidGuard-1.3/src'
make: *** [all] Error 1

La soluzione è semplice:
[root@proxy squidGuard-1.3]# yum install flex
[root@proxy squidGuard-1.3]# make clean
[root@proxy squidGuard-1.3]# ./configure
[root@proxy squidGuard-1.3]# make
[root@proxy squidGuard-1.3]# make install

Problema risolto!!!