Jbuilder support for multiple test executables

[bcc32]

@lambda_foo

(alias
 ((name runtest)
  (package webmachine)
  (deps (test_logic.exe))
  (action (run ${<}))))

(alias
 ((name runtest)
  (package webmachine)
  (deps (test_dispatch.exe))
  (action (run ${<}))))

${<} expands to only the first listed dependency [0]. You can use ${^} to refer to all dependencies.

[0] https://jbuilder.readthedocs.io/en/latest/jbuild.html#variables-expansion