my linux server is redhat AS 3 update 5.

I download dovecot 0.99.11 source rpm to rebuild a binary rpm package

I issued command rpmbuild -ba dovecot.spec

after a few mins of works, rpmbuild process stopped with errors

..............

gcc -DHAVE_CONFIG_H -I. -I. -I../..     -O2 -g -pipe -march=i386 -mcpu=i686 -Wall -W -Wmissing-prototypes -Wmissing-declarations -Wpointer-arith -Wchar-subscripts -Wformat=2 -Wbad-function-cast -I/usr/kerberos/include    -c unlink-lockfiles.c
gcc -DHAVE_CONFIG_H -I. -I. -I../..     -O2 -g -pipe -march=i386 -mcpu=i686 -Wall -W -Wmissing-prototypes -Wmissing-declarations -Wpointer-arith -Wchar-subscripts -Wformat=2 -Wbad-function-cast -I/usr/kerberos/include    -c utc-offset.c
gcc -DHAVE_CONFIG_H -I. -I. -I../..     -O2 -g -pipe -march=i386 -mcpu=i686 -Wall -W -Wmissing-prototypes -Wmissing-declarations -Wpointer-arith -Wchar-subscripts -Wformat=2 -Wbad-function-cast -I/usr/kerberos/include    -c utc-mktime.c
gcc -DHAVE_CONFIG_H -I. -I. -I../..     -O2 -g -pipe -march=i386 -mcpu=i686 -Wall -W -Wmissing-prototypes -Wmissing-declarations -Wpointer-arith -Wchar-subscripts -Wformat=2 -Wbad-function-cast -I/usr/kerberos/include    -c var-expand.c
gcc -DHAVE_CONFIG_H -I. -I. -I../..     -O2 -g -pipe -march=i386 -mcpu=i686 -Wall -W -Wmissing-prototypes -Wmissing-declarations -Wpointer-arith -Wchar-subscripts -Wformat=2 -Wbad-function-cast -I/usr/kerberos/include    -c write-full.c
rm -f liblib.a
make[3]: AR@: Command not found
make[3]: *** [liblib.a] Error 127
make[3]: Leaving directory `/usr/src/redhat/BUILD/dovecot-0.99.11/src/lib'
make[2]: *** [all-recursive] Error 1
make[2]: Leaving directory `/usr/src/redhat/BUILD/dovecot-0.99.11/src'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/usr/src/redhat/BUILD/dovecot-0.99.11'
make: *** [all-recursive-am] Error 2
error: Bad exit status from /var/tmp/rpm-tmp.11388 (%build)

RPM build errors:
    Bad exit status from /var/tmp/rpm-tmp.11388 (%build)

What's the meaning of these errors ?