Add build utility commands

* `build` is an alias which on first use invokes `build-dir --build` to
  select a build directory, reconfigure the `build` alias, and invoke
  the `build` alias on the selected build directory.
* `debug` is an alias to the installed system native debugger.
* `build-dir` is a function to select a build directory by reconfiguring
  the `build` alias, it detects `build.ninja` or `Makefile` in the build
  directory and selects the appropriate `ninja` or `make` command.
  Depends on the `build-dir.py` Python script which uses the `pick`
  package to interactively select the build directory.
* `build-run` is a function which builds the specified target then
  attempts to run it, making the assumption it resides in the `bin`
  subdirectory of the build directory.
* `build-debug` is a function which build the specified tared then
  attempts to debug it using the system native debugger, making the
  assumption it resides in the `bin` subdirectory of the build
  directory.

.conduit.yaml

@@ -20,4 +20,6 @@
     - https://github.com/zsh-users/zsh-autosuggestions.git
     - https://github.com/zsh-users/zsh-history-substring-search.git
     - https://github.com/zsh-users/zsh-syntax-highlighting.git
+- pip:
+    - --user pick
 - message: zsh will be the default prompt after next login