chore(tooling): Fixup Flake details, flesh out comments

pkg.nix

@@ -29,7 +29,6 @@ let
   luaEnv = lua.withPackages(ps: with ps; [
     cassowary
     cldr
-    cosmo
     fluent
     linenoise
     loadkit
@@ -99,15 +98,20 @@ in stdenv.mkDerivation (finalAttrs: {
 
   configureFlags = [
     "--with-system-luarocks"
-    # TODO: Explain this flag
+    # The automake check target uses `pdfinfo` to confirm the output of a test
+    # run. This flake build eschews that test because it is run from the source
+    # directory but the binary is already built with system paths, so it can't
+    # be checked under Nix until after install. By specifying some binary here
+    # we skip the configure time test for `pdfinfo`, by using `false` we make
+    # sure that check fails if run (which we don't).
     "PDFINFO=false"
     #"--with-manual" In Nixpkgs we add this flag, here its not important enough
   ] ++ lib.optionals lua.pkgs.isLuaJIT [
     "--with-luajit"
   ];
 
   postPatch = ''
-    patchShebangs build-aux/*.sh
+    patchShebangs build-aux/*.sh build-aux/git-version-gen
   '' + lib.optionalString stdenv.isDarwin ''
     sed -i -e 's|@import AppKit;|#import <AppKit/AppKit.h>|' src/macfonts.m
   '';