feat(3p/nix): Add installCheckPhase

Add an installCheckPhase that runs the appropriate substituteAll on
common.sh and runs the lang.sh tests with the build artifacts in the
PATH.

Change-Id: I2df5a93b8f3ffdfdc194a0e7d6b6669ef520c345
Reviewed-on: https://cl.tvl.fyi/c/depot/+/561
Reviewed-by: glittershark <grfn@gws.fyi>

third_party/default.nix

@@ -126,6 +126,7 @@ let
       texlive
       thttpd
       tree
+      utillinux
       which
       writeShellScript
       writeShellScriptBin

third_party/nix/default.nix

@@ -48,11 +48,24 @@ in pkgs.llvmPackages.libcxxStdenv.mkDerivation {
     xz
   ];
 
+  installCheckInputs = with pkgs; [
+    utillinux
+  ];
+
   propagatedBuildInputs = with pkgs; [
     boost
     largeBoehm
   ];
 
+  doInstallCheck = true;
+
+  installCheckPhase = ''
+    export PATH=$out/bin:$PATH
+    cd ../tests/
+    substituteAll common.sh.in common.sh
+    bash lang.sh
+  '';
+
   # Install the various symlinks to the Nix binary which users expect
   # to exist.
   postInstall = ''