I am having trouble building mysql on netbsd1.6 , its the same problem
trying to build mysql 4.0.8 or 3.23.54

gcc -v
Configured with:
/home/src/gcc-3.2.1/configure --enable-languages=c,c++ --enable-threads=posi
x --enable-conept-checks --enable-c99 --enable-cstdlib
Thread model: posix
gcc version 3.2.1

CXXFLAGS=-O3 -felide-constructors -fno-exceptions  -fno-rtti

mysql configurations
./configure --program-prefix=mysql --enable-assambler -without-innodb --with
-pthread --enable-thread-safe-client
.....
checking for pthread_sigmask... yes
checking for pthread_setprio... no
checking for pthread_setprio_np... no
checking for pthread_setschedparam... yes
checking for pthread_attr_setprio... no
checking for pthread_attr_setschedparam... yes
checking for pthread_attr_create... no
checking for pthread_getsequence_np... no
checking for pthread_attr_setstacksize... yes
checking for pthread_condattr_create... no
checking for rwlock_init... no
checking for pthread_rwlock_rdlock... yes
.....

Also i have pth-1.4.1nb2 installed

The compiler error is as follows:
gcc -DDEFAULT_CHARSET_HOME=\"/usr/local\" -DDATADIR=\"/usr/local/var\" -DSHA
REDIR=\"/usr/local/share/mysql\" -DDONT_USE_RAID -I. -I. -I.. -I./../include
 -I../include -I./.. -I.. -I.. -O3 -DDBUG_OFF -O3 -Dunix -c my_pthread.c -MT
my_pthread.lo -MD -MP -MF .deps/my_pthread.TPlo  -fPIC -DPIC -o
.libs/my_pthread.lo
my_pthread.c: In function `my_pthread_setprio':
my_pthread.c:38: storage size of `tmp_sched_param' isn't known
my_pthread.c:41: `SCHED_OTHER' undeclared (first use in this function)
my_pthread.c:41: (Each undeclared identifier is reported only once
my_pthread.c:41: for each function it appears in.)
my_pthread.c: In function `my_pthread_getprio':
my_pthread.c:50: storage size of `tmp_sched_param' isn't known
my_pthread.c: In function `my_pthread_attr_setprio':
my_pthread.c:67: storage size of `tmp_sched_param' isn't known

It seemes mysql tries to build its own versions of some of these functions
that are missing but breaks in the process.  Anyone have this problem ?