binary snapshot install crashes on ps docs

[Chuck Adams]

The lack of ps documentation in the snapshot builds causes 'make
install' to exit ungracefully.   Granted it's the last step so it's
harmless, but it looks like things failed.

To wit:

if test -d share/html ; then cp -r share/html/*
/biztools/pkg/ghc-6.5.20060105/share/ghc-6.5.20060105/html ; fi
for i in share/*.ps; do \
        cp $i /biztools/pkg/ghc-6.5.20060105/share/ghc-6.5.20060105 ; \
done
cp: cannot stat `share/*.ps': No such file or directory
make: *** [install-docs] Error 1