configure: error: C compiler cannot create executables

[Stefanita Rares Dumitrescu]

Hi guys,  i have a problem over here.

I can't upgrade any packages because i am getting "configure: error: C 
compiler cannot create executables"

Here's the part where it fails from config.log.

configure:3448: checking whether the C compiler works
configure:3470: cc -I/usr/local/include -O2 -pipe -fno-strict-aliasing   
-Wl,-rpath,/usr/lib:/usr/local/lib -pthread conftest.c -L/usr/local/lib  
-Wl,-rpath,/usr/lib:/usr/local/lib -pthread >&5
/usr/lib/libpthread.so: undefined reference to 
`__elf_phdr_match_addr at FBSDprivate_1.0'
configure:3474: $? = 1
configure:3512: result: no
configure: failed program was:
| /* confdefs.h */
| #define PACKAGE_NAME ""
| #define PACKAGE_TARNAME ""
| #define PACKAGE_VERSION ""
| #define PACKAGE_STRING ""
| #define PACKAGE_BUGREPORT ""
| #define PACKAGE_URL ""
| #define CANONICALIZATION_FOR_MATHN 1
| /* end confdefs.h.  */
|
| int
| main ()
| {
|
|   ;
|   return 0;
| }
configure:3517: error: in `/usr/ports/lang/ruby19/work/ruby-1.9.3-p484':
configure:3520: error: C compiler cannot create executables
See `config.log' for more details

The thing with this system is: i was using a custom kernel, and i tried 
to upgrade to freebsd 8.4 from 8.3. I didn't realise that the kernel did 
not get upgraded after the freebsd-update utility ran, and i am still 
running the 8.3 kernel but seemingly on a 8.4 system.

I can't recompile world/kernel right now because it errors out at pthreads.

Do you have any idea on what could i do to get the system back in shape 
? The thing is i am cautious with this, since it's a production server.

The thing is i have upgraded about 13 other machines from either 8.3 to 
8.4 or 9.0->9.2 without issues, and only this one borked out.