(gcc-4.1.2, GNU Make 3.81) USE="nptl -X" /dev-lang/mono-1.2.4 のコンパイル中に止まってしまいます (busy-loop)。
(前略)
make[3]: Entering directory `/var/tmp/portage/dev-lang/mono-1.2.4/work/mono-1.2.4/runtime'
test -n '_tmpinst/bin/ilasmilasm/ilasm.exe'
echo '#! /bin/sh' > _tmpinst/bin/ilasm
r=`pwd`; m=`cd ../mcs && pwd`; echo 'exec "'"$r/_tmpinst/bin/mono"'" "'"$m/ilasm/ilasm.exe"'" "$@"' >> _tmpinst/bin/ilasm
chmod +x _tmpinst/bin/ilasm
make[3]: Leaving directory `/var/tmp/portage/dev-lang/mono-1.2.4/work/mono-1.2.4/runtime'
make test-support-file target=_tmpinst/bin/gmcs file=gmcs/gmcs.exe
make[3]: Entering directory `/var/tmp/portage/dev-lang/mono-1.2.4/work/mono-1.2.4/runtime'
test -n '_tmpinst/bin/gmcsgmcs/gmcs.exe'
echo '#! /bin/sh' > _tmpinst/bin/gmcs
r=`pwd`; m=`cd ../mcs && pwd`; echo 'exec "'"$r/_tmpinst/bin/mono"'" "'"$m/gmcs/gmcs.exe"'" "$@"' >> _tmpinst/bin/gmcs
chmod +x _tmpinst/bin/gmcs
make[3]: Leaving directory `/var/tmp/portage/dev-lang/mono-1.2.4/work/mono-1.2.4/runtime'
if test -w ../mcs; then :; else chmod -R +w ../mcs; fi
cd ../mcs && make PROFILES='default net_2_0' CC='i686-pc-linux-gnu-gcc' all-profiles
make[3]: Entering directory `/var/tmp/portage/dev-lang/mono-1.2.4/work/mono-1.2.4/mcs'
make profile-do--default--all profile-do--net_2_0--all
make[4]: Entering directory `/var/tmp/portage/dev-lang/mono-1.2.4/work/mono-1.2.4/mcs'
make PROFILE=basic all
make[5]: Entering directory `/var/tmp/portage/dev-lang/mono-1.2.4/work/mono-1.2.4/mcs'
(ここで止まる)

エラーを吐いたりはしません。状況を打開する方法を御存知の方いらっしゃいませんでしょうか。