Adding client.mk options from /cygdrive/c/home/tom/MOZCONFIG:
    MOZ_OBJDIR=/cygdrive/c/home/tom/moz.obj
    MOZ_CO_PROJECT=browser
    MOZ_MAKE_FLAGS=CC='distcc cl' CXX='distcc cl' -j4
make CC='distcc cl' CXX='distcc cl' -j4 -C /cygdrive/c/home/tom/moz.obj
make[1]: Entering directory `/cygdrive/c/home/tom/moz.obj'
rm -f -rf ./dist/sdk
rm -f -rf ./dist/include
/usr/bin/make -C config export
make[2]: Entering directory `/cygdrive/c/home/tom/moz.obj/config'
/usr/bin/perl -I/cygdrive/c/home/tom/mozilla/config /cygdrive/c/home/tom/mozilla/config/bdate.pl build_number 
make[3]: Entering directory `/cygdrive/c/home/tom/moz.obj/config/mkdepend'
make[3]: Nothing to be done for `export'.
make[3]: Leaving directory `/cygdrive/c/home/tom/moz.obj/config/mkdepend'
/cygdrive/c/home/tom/mozilla/build/cygwin-wrapper /cygdrive/c/proj/vc8-moztools/bin/nsinstall -m 644 nsBuildID.h ../mozilla-config.h /cygdrive/c/home/tom/mozilla/config/nsStaticComponents.h  ../dist/include
rm -f ../config/final-link-comps ../config/final-link-libs ../config/final-link-comp-names
rm -f ../dist/bin/chrome/chromelist.txt
/cygdrive/c/home/tom/mozilla/build/cygwin-wrapper /cygdrive/c/proj/vc8-moztools/bin/nsinstall -t -m 644 nsBuildID.h ../mozilla-config.h /cygdrive/c/home/tom/mozilla/config/nsStaticComponents.h  ../dist/sdk/include
make[2]: Leaving directory `/cygdrive/c/home/tom/moz.obj/config'
/usr/bin/make nspr
make[2]: Entering directory `/cygdrive/c/home/tom/moz.obj'
/usr/bin/make -C nsprpub
make[3]: Entering directory `/cygdrive/c/home/tom/moz.obj/nsprpub'
cd config; /usr/bin/make -j1 export
make[4]: Entering directory `/cygdrive/c/home/tom/moz.obj/nsprpub/config'
make[4]: warning: -jN forced in submake: disabling jobserver mode.
distcc cl -Fonow.obj -c      -W3 -nologo -GF -Gy -Od -MD   -UDEBUG -U_DEBUG -UWINNT  -DMOZILLA_CLIENT=1 -DNDEBUG=1 -DXP_PC=1 -DWIN32=1 -DWIN95=1 -D_PR_GLOBAL_THREADS_ONLY=1 -D_X86_=1  -DFORCE_PR_LOG   /cygdrive/c/home/tom/mozilla/nsprpub/config/now.c
cl : Command line warning D9002 : ignoring unknown option '/cygdrive/c/home/tom/mozilla/nsprpub/config/now.c'
cl : Command line error D8003 : missing source filename
make[4]: *** [now.obj] Error 2
make[4]: Leaving directory `/cygdrive/c/home/tom/moz.obj/nsprpub/config'
make[3]: *** [export] Error 2
make[3]: Leaving directory `/cygdrive/c/home/tom/moz.obj/nsprpub'
make[2]: *** [nspr] Error 2
make[2]: Leaving directory `/cygdrive/c/home/tom/moz.obj'
make[1]: *** [default] Error 2
make[1]: Leaving directory `/cygdrive/c/home/tom/moz.obj'
make: *** [build] Error 2