spark2014: fix incomplete install (#208830)

The previous installPhase was only using `make install`, while the real
target needed is `make install-all`. This installs many missing tools
under `$out/libexec/`, such as the missing `gnatwhy3` binary, which was
the root cause of #208830.

With this, gnatprove can now successfully discharge and prove things
with solvers like Z3, etc.

And, because it also includes `why3server`, we don't need to use
wrapProgram on it anymore, either!

Closes #208830

Signed-off-by: Austin Seipp <[e-mail]>

pkgs/development/libraries/ada/spark2014/default.nix

···
 , gnatcoll-core
 , gprbuild
 , python3
-, why3
 , ocaml
 , ocamlPackages
 , makeWrapper
···
     make setup
   '';
 
-  postInstall = ''
+  installPhase = ''
+    make install-all
     cp -a ./install/. $out
-    # help gnatprove to locate why3server
-    wrapProgram "$out/bin/gnatprove" \
-        --prefix PATH : "${why3}/lib/why3"
   '';
 
   meta = with lib; {