I've got severals warnings : 

 * [UFO] src/client/cl_inventory.c
 * [UFO] src/client/cl_input.c
 * [UFO] src/client/cl_irc.c
src/client/cl_irc.c: In function `Irc_Proto_Quit':
src/client/cl_irc.c:200: warning: implicit declaration of function `snprintf'
 * [UFO] src/client/cl_keys.c
 * [UFO] src/client/cl_le.c
 * [UFO] src/client/cl_main.c
src/client/cl_main.c: In function `CL_SendConnectPacket':
src/client/cl_main.c:320: warning: implicit declaration of function `htons'

htons is defined on solaris in
     #include <netinet/in.h>
and snprintf in <stdio.h>

 * [UFO] src/qcommon/common.c
src/qcommon/common.c: In function `Qcommon_LocaleInit':
src/qcommon/common.c:571: warning: implicit declaration of function `unsetenv'


 * [UFO] src/game/q_shared.c
src/game/q_shared.c: In function `Q_putenv':
src/game/q_shared.c:1875: warning: implicit declaration of function `putenv'
src/game/q_shared.c: In function `Q_stricmp':
src/game/q_shared.c:1937: warning: implicit declaration of function `strcasecmp'
src/game/q_shared.c: In function `Q_vsnprintf':
src/game/q_shared.c:4356: warning: implicit declaration of function `vsnprintf'

strcasecmp is defined in <strings.h>
vsnprintf is defined in <stdio.h> and <stdarg.h>
putenv is defined in <stdlib.h>

 * [UFO] src/ports/solaris/sys_solaris.c
src/ports/solaris/sys_solaris.c: In function `Sys_GetCurrentUser':
src/ports/solaris/sys_solaris.c:197: warning: implicit declaration of function `getpwuid'
src/ports/solaris/sys_solaris.c:197: warning: assignment makes pointer from integer without a cast
src/ports/solaris/sys_solaris.c:200: error: dereferencing pointer to incomplete type
gmake: *** [debug-solaris-i386/client/ports/solaris/sys_solaris.o] Error 1
I've added #include <pwd.h> in sys_solaris.c


 * [UFO] src/ports/unix/net_udp.c
src/ports/unix/net_udp.c: In function `NET_Socket':
src/ports/unix/net_udp.c:669: error: `FIONBIO' undeclared (first use in this function)
src/ports/unix/net_udp.c:669: error: (Each undeclared identifier is reported only once
src/ports/unix/net_udp.c:669: error: for each function it appears in.)
src/ports/unix/net_udp.c:683: warning: implicit declaration of function `strcasecmp'
gmake: *** [debug-solaris-i386/client/ports/unix/net_udp.o] Error 1

I've added #include <sys/filio.h> in net_udp.c

 

At the moment, I've thoses errors : 
ld: fatal: symbol `Sys_GetCurrentUser' is multiply-defined:
        (file debug-solaris-i386/client/ports/solaris/sys_solaris.o type=FUNC; file debug-solaris-i386/client/ports/unix/sys_unix.o type=FUNC);
ld: fatal: symbol `Sys_Cwd' is multiply-defined:
        (file debug-solaris-i386/client/ports/solaris/sys_solaris.o type=FUNC; file debug-solaris-i386/client/ports/unix/sys_unix.o type=FUNC);
ld: fatal: symbol `Sys_FileTime' is multiply-defined:
        (file debug-solaris-i386/client/ports/solaris/sys_solaris.o type=FUNC; file debug-solaris-i386/client/ports/unix/sys_unix.o type=FUNC);
ld: fatal: symbol `Sys_NormPath' is multiply-defined:
        (file debug-solaris-i386/client/ports/solaris/sys_solaris.o type=FUNC; file debug-solaris-i386/client/ports/unix/sys_unix.o type=FUNC);
ld: fatal: symbol `Sys_OSPath' is multiply-defined:
        (file debug-solaris-i386/client/ports/solaris/sys_solaris.o type=FUNC; file debug-solaris-i386/client/ports/unix/sys_unix.o type=FUNC);
ld: fatal: symbol `Sys_AppActivate' is multiply-defined:
        (file debug-solaris-i386/client/ports/solaris/sys_solaris.o type=FUNC; file debug-solaris-i386/client/ports/unix/sys_unix.o type=FUNC);
ld: fatal: symbol `Sys_UnloadGame' is multiply-defined:
        (file debug-solaris-i386/client/ports/solaris/sys_solaris.o type=FUNC; file debug-solaris-i386/client/ports/unix/sys_unix.o type=FUNC);
ld: fatal: symbol `Sys_GetGameAPI' is multiply-defined:
        (file debug-solaris-i386/client/ports/solaris/sys_solaris.o type=FUNC; file debug-solaris-i386/client/ports/unix/sys_unix.o type=FUNC);
ld: fatal: File processing errors. No output written to ufo