Can't search the forum at this time so it's possible this bug was already submitted earlier.
Everything is latest version (tc 3.5.1, all tcz's, ...)
If you install compiletc the permissions on the /tmp directory change
Directly copy-pasted from the console:
~ $ ls -l / | grep tmp
drwxrwxrwt 6 root staff 180 Mar 19 11:37 tmp
~ $ tce-load -i /mnt/win/bartel/devpack/compiletc.tcz
sed.tcz: OK
pkg-config.tcz: OK
patch.tcz: OK
make.tcz: OK
m4.tcz: OK
grep.tcz: OK
gperf.tcz: OK
gmp.tcz: OK
ppl.tcz: OK
mpfr.tcz: OK
cloog.tcz: OK
gcc_libs.tcz: OK
gcc.tcz: OK
gawk.tcz: OK
flex.tcz: OK
findutils.tcz: OK
diffutils.tcz: OK
bison.tcz: OK
base-dev.tcz: OK
binutils.tcz: OK
compiletc.tcz: OK
~ $ ls -l / | grep tmp
drwxr-sr-x 6 tc staff 200 May 16 2010 tmp
If you run as user tc you will not notice much, but if you are logged on with another id, you lose write access to the temp directory.