Rescue me!!! Tripwire-portable-0.9 err...kind of strange...

pikestone

i got the following err while "make install" the Tripwire-portable-0.9 package, following the blfs book v6.1

===============================================
This General Public License does not permit incorporating your program into
proprietary programs.  If your program is a subroutine library, you may
consider it more useful to permit linking proprietary applications with the
library.  If this is what you want to do, use the GNU Library General
Public License instead of this License.


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Using configuration file ./install/install.cfg

Checking for programs specified in install configuration file....

/usr/local/bin:/bin:/usr/bin:/usr/libexec -oi -t does not exist.  Exiting.
make[3]: *** [install-data-hook] Error 1
make[3]: Leaving directory `/usr/src/packagesAndPatches_all/tripwire-portable-0.9'
make[2]: *** [install-data-am] Error 2
make[2]: Leaving directory `/usr/src/packagesAndPatches_all/tripwire-portable-0.9'
make[1]: *** [install-am] Error 2
make[1]: Leaving directory `/usr/src/packagesAndPatches_all/tripwire-portable-0.9'
make: *** [install-recursive] Error 1
===============================================

as the err message indicated, i viewed the ./install/install.cfg file,
and the corresbonding line is:

TWMAILPROGRAM="${path_to_sendmail} -oi -t"

so "${path_to_sendmail}"
is
"/usr/local/bin:/bin:/usr/bin:/usr/libexec" here,
and as the message indicating "Checking for programs specified in install configuration file....",
here i don't think "/usr/local/bin:/bin:/usr/bin:/usr/libexec" looks like a "program", kind of strange, huh?

can anybody please tell me what on earth was the err caused by?
and the solution is also greatly appreciated...thanx in advance...

ps: i can ensure the integrity of the package downloaded based on the md5sum...