Compiling php-4.2.1 on sparc solaris 2.7 using gcc and gnu tools gives the following error:

./configure --with-oci8=/usr/local/OraHome1 --enable-track-vars --with-mysql=/usr/local/mysql --with-apxs=/usr/local/apache/bin/apxs --enable-sigchild

(showing only unix.h entries):
checking for unix.h... yes
checking for unix.h... (cached) yes

running make gives:
Making all in Zend
/bin/sh ../libtool --silent --mode=compile gcc -DHAVE_CONFIG_H -I. -I. -I../main   -D_POSIX_PTHREAD_SEMANTICS -DSOLARIS2=270 -I../TSRM  -g -O2 -prefer-pic -c -o zend_language_parser.lo `test -f zend_language_parser.c || echo './'`zend_language_parser.c
In file included from zend_compile.h:24,
                 from zend_language_parser.c:147:
zend.h:55:19: unix.h: No such file or directory
make: *** [zend_language_parser.lo] Error 1
*** Error code 1
make: Fatal error: Command failed for target `all-recursive'

"find / -name unix.h" shows no unix.h on the system!

The exact same system compiles 4.1.2 and 4.2.0 with no problems.