After doing make install on apache 1.3.9 and compiling, when the linking of apache
is being done:
cd ..; cc "-Ae" -I.  -I/store/lib/perl5/PA-RISC1.1/5.00404/CORE     helpers/dummy.c -o helpers/dummy   -L/store/lib -Lmodules/php4 -L../modules/php4 -L../../modules/php4 -lmodphp4 -L/store/store/bise04/php/src-991004-hp700ux10/ext/pcre/pcrelib -lpcre -L/store/store/bise04/php/src-991004-hp700ux10/regex -lregex   -lcrypt -L/store/lib -lgd -lifsql -lifasf -lifgen -lifos -lifgls -lnsl_s -lV3 -lcl -lsec /app/informix/lib/esql/checkapi.o -lifglx -L/app/informix/lib -L/app/informix/lib/esql     -lm    -Wl,-E -Wl,-B,deferred   -L/usr/local/lib /store/lib/perl5/PA-RISC1.1/5.00404/auto/DynaLoader/DynaLoader.a -L/store/lib/perl5/PA-RISC1.1/5.00404/CORE -lperl -lnet -lnsl_s -lndbm -ldld -lm -lc -lndir -lcrypt 
/usr/ccs/bin/ld: Can't find library for -lifsql

As can be seen, it's not able to find the Infomix libraries as they are specified before "-L/app/informix/lib -L/app/informix/lib/esql"

These options comes from the sapi/apache/libphp4.module file
Name: php4_module
ConfigStart
        RULE_WANTHSREGEX=yes
        LIBS=" -L/store/lib -Lmodules/php4 -L../modules/php4 -L../../modules/php
4 -lmodphp4 -L/store/store/bise04/php/src-991004-hp700ux10/ext/pcre/pcrelib -lpc
re -L/store/store/bise04/php/src-991004-hp700ux10/regex -lregex  `/store/store/b
ise04/php/src-991004-hp700ux10/libzend/zend_config --libs` -lcrypt -L/store/lib 
-lgd -lifsql -lifasf -lifgen -lifos -lifgls -lnsl_s -lV3 -lcl -lsec /app/informi
x/lib/esql/checkapi.o -lifglx -L/app/informix/lib -L/app/informix/lib/esql     -
lm   $LIBS"
        RULE_HIDE=yes
        CFLAGS="$CFLAGS -I/store/store/bise04/php/src-991004-hp700ux10 -I/store/
store/bise04/php/src-991004-hp700ux10/libzend -I/store/store/bise04/php/src-9910
04-hp700ux10/libzend -I/store/store/bise04/php/src-991004-hp700ux10"
ConfigEnd