Unable to make PostgreSQL 6.5.3 on Caldera Linux 2.2: undefined reference to 'crypt'

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POSTGRESQL BUG REPORT TEMPLATE
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Your name: Gord Tomlin
Your email address: gordt(at)actionsoftware(dot)com

System Configuration
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Architecture: Intel Pentium 90, 64 Mb

Operating System: Caldera OpenLinux 2.2

PostgreSQL version: PostgreSQL-6.5.3

Compiler used: gcc version egcs-2.91.66 19990314 (egcs-1.1.2 release)

Please enter a FULL description of your problem:
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Make fails with the following:

gcc -o postgres access/SUBSYS.o bootstrap/SUBSYS.o catalog/SUBSYS.o
commands/SUBSYS.o executor/SUBSYS.o lib/SUBSYS.o libpq/SUBSYS.o
main/SUBSYS.o parser/SUBSYS.o nodes/SUBSYS.o optimizer/SUBSYS.o
port/SUBSYS.o postmaster/SUBSYS.o regex/SUBSYS.o rewrite/SUBSYS.o
storage/SUBSYS.o tcop/SUBSYS.o utils/SUBSYS.o
../utils/version.o -lnsl -ldl -lm -export-dynamic
libpq/SUBSYS.o: In function `crypt_verify':
libpq/SUBSYS.o(.text+0x3a64): undefined reference to `crypt'
libpq/SUBSYS.o: In function `verify_password':
libpq/SUBSYS.o(.text+0x3ca7): undefined reference to `crypt'
make[1]: *** [postgres] Error 1
make[1]: Leaving directory `/usr/src/pgsql/postgresql-6.5.3/src/backend'
make: *** [all] Error 2

Please describe a way to repeat the problem. Please try to provide a
concise reproducible example, if at all possible:
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Just try to run the makefile.

If you know how this problem might be fixed, list the solution below:
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