This appears to be very similar to bud id 7162.  I edited
the php_config.h and set both HAVE_POSIX_READDIR_R and
HAVE_OLD_READDIR_R to undef and all components build
successfully.  I tried this after reading the follow up
comment in bug id 7162.

These are the configuration options:
./configure --prefix=/float/php_4.0.6 \
--with-gdbm=/float \
--with-apxs=/float/apache_1.3.20/bin/apxs \
--with-config-file-path=/float/php_4.0.6/etc \
--without-mysql

Here's the compile line and the error message:
/bin/sh /export/apache/php-4.0.6/libtool --silent --mode=compile gcc  -I. 
-I/export/apache/php-4.0.6/main -I/export/apache/php-4.0.6/main 
-I/export/apache/php-4.0.6 
-I/float/apache_1.3.20/include -I/export/apache/php-4.0.6/Zend 
-I/float/include -I/export/apache/php-4.0.6/ext/xml/expat/xmltok -I/export/apache/php-4.0.6/ext/xml/expat/xmlparse -I/export/php-4.0.6/TSRM  -D_POSIX_PTHREAD_SEMANTICS -DSOLARIS2=280 -DUSE_EXPAT -DSHARED_CORE -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -DSUPPORT_UTF8 -DXML_BYTE_ORDER=21 -g -O2  -c reentrancy.c
reentrancy.c: In function `php_readdir_r':
reentrancy.c:109: too few arguments to function `readdir64_r'
*** Error code 1
make: Fatal error: Command failed for target `reentrancy.lo'
Current working directory /export/workspace/d11/cmckee/apache/php-4.0.6/main
*** Error code 1
make: Fatal error: Command failed for target `all-recursive'