[racket-dev] build: schemef.h -> schemex.h

The ubuntu ppa build has been failing for a while, and I finally tracked it down to this issue: src/racket/src/schemef.h has a newer timestamp than src/racket/src/schemex.h on a fresh git checkout from github. This results in the make system trying to execute the following

make[6]: Entering directory `/home/jon/tmp/plt2/src/b/racket/src'
racket ../../../racket/src/makex.rkt < ../../../racket/src/schemef.h > ../../../racket/src/schemex.h

On a fresh machine with no racket installed, this fails because there is no 'racket' executable available. I'm not sure what the best solution is. Right now I'm thinking of just doing a 'touch *' immediately after a 'git pull' for the build machine, since schemex.h probably should not be built every time.. But in general I imagine someone might run into this issue on their own machine. I'm mildly surprised it hasn't happened to anyone yet.

For whatever reason, this issue only started appearing about 3 weeks ago. Perusing the git log doesn't show much related to schemex.h or whatever so I'm not sure what the root cause is.