I got a bit further by building like:

make BUILD=car2 ARCH=pc CC=gcc-2.95 emptool

but then it fell over with

../../lib/pc-generic-debug2/libempeg_protocol.a(discovery.o)(.gnu.linkonce.t._ZN9CNgLogHexC2EPKcS1_iN6CNgLog8LogLevelE+0x16): In function `CNgLogHex::CNgLogHex[not-in-charge](char const*, char const*, int, CNgLog::LogLevel)':
/usr/include/c++/3.2/i386-linux/bits/gthr-default.h:484: undefined reference to `CNgLog::CNgLog[not-in-charge](char const*, char const*, int, CNgLog::LogLevel)'
../../lib/pc-generic-debug2/libempeg_protocol.a(discovery.o)(.gnu.linkonce.t._ZN9CNgLogHexC1EPKcS1_iN6CNgLog8LogLevelE+0x16): In function `CNgLogHex::CNgLogHex[in-charge](char const*, char const*, int, CNgLog::LogLevel)':
/usr/include/c++/3.2/i386-linux/bits/gthr-default.h:484: undefined reference to `CNgLog::CNgLog[not-in-charge](char const*, char const*, int, CNgLog::LogLevel)'

(and more). Looks like the libc or libstdc++ version comes into it as well, and I don't know how to override that.

The pre-built tools work for me, and I'm not planning any hacking on these, so it's not an urgent issue.