see if nix provided libpq reproduces segfault

It doesn't seem to

```
~/org-roam/data/42/66517f-9ddf-40fd-b8c1-7b444364dc1b/th-pq-segfault $ haskell-language-server-wrapper
Found "/home/cody/org-roam/data/42/66517f-9ddf-40fd-b8c1-7b444364dc1b/th-pq-segfault/hie.yaml" for "/home/cody/org-roam/data/42/66517f-9ddf-40fd-b8c1-7b444364dc1b/th-pq-segfault/a"
Module "/home/cody/org-roam/data/42/66517f-9ddf-40fd-b8c1-7b444364dc1b/th-pq-segfault/a" is loaded by Cradle: Cradle {cradleRootDir = "/home/cody/org-roam/data/42/66517f-9ddf-40fd-b8c1-7b444364dc1b/th-pq-segfault", cradleOptsProg = CradleAction: Stack}
Run entered for haskell-language-server-wrapper(haskell-language-server-wrapper) Version 1.1.0.0 x86_64 ghc-8.10.4
Current directory: /home/cody/org-roam/data/42/66517f-9ddf-40fd-b8c1-7b444364dc1b/th-pq-segfault
Operating system: linux
Arguments: []
Cradle directory: /home/cody/org-roam/data/42/66517f-9ddf-40fd-b8c1-7b444364dc1b/th-pq-segfault
Cradle type: Stack

Tool versions found on the $PATH
cabal:		3.4.0.0
stack:		2.7.1
ghc:		8.10.4

Consulting the cradle to get project GHC version...
Project GHC version: 8.10.4
haskell-language-server exe candidates: ["haskell-language-server-8.10.4","haskell-language-server-8.10","haskell-language-server"]
Launching haskell-language-server exe at:/run/current-system/sw/bin/haskell-language-server-8.10.4
haskell-language-server version: 1.1.0.0 (GHC: 8.10.4) (PATH: /nix/store/nr5rrd8slk8limz0yk2yrzcqv4vf1k6y-haskell-language-server-1.1.0.0/bin/haskell-language-server)
 ghcide setup tester in /home/cody/org-roam/data/42/66517f-9ddf-40fd-b8c1-7b444364dc1b/th-pq-segfault.
Report bugs at https://github.com/haskell/haskell-language-server/issues

Step 1/4: Finding files to test in /home/cody/org-roam/data/42/66517f-9ddf-40fd-b8c1-7b444364dc1b/th-pq-segfault
Found 3 files

Step 2/4: Looking for hie.yaml files that control setup
Found 1 cradle
  (/home/cody/org-roam/data/42/66517f-9ddf-40fd-b8c1-7b444364dc1b/th-pq-segfault/hie.yaml)

Step 3/4: Initializing the IDE

Step 4/4: Type checking the files
2021-06-25 21:40:11.816452004 [ThreadId 82] INFO hls:	Consulting the cradle for "pqexample/src/PQ.hs"
Output from setting up the cradle Cradle {cradleRootDir = "/home/cody/org-roam/data/42/66517f-9ddf-40fd-b8c1-7b444364dc1b/th-pq-segfault", cradleOptsProg = CradleAction: Stack}
> Configuring GHCi with the following packages: pqexample
> /home/cody/org-roam/data/42/66517f-9ddf-40fd-b8c1-7b444364dc1b/th-pq-segfault/.stack-work/install/x86_64-linux-nix/bf9fd1ff1ae588cb8e642dd7bbc8c5b1299cd10a51c5a3ada44fa584d7a449e0/8.10.4/pkgdb:/home/cody/.stack/snapshots/x86_64-linux-nix/bf9fd1ff1ae588cb8e642dd7bbc8c5b1299cd10a51c5a3ada44fa584d7a449e0/8.10.4/pkgdb:/nix/store/d8mbb3cjp24qi0mcwb0rkmw3jhl91rjc-ghc-8.10.4/lib/ghc-8.10.4/package.conf.d
2021-06-25 21:40:18.482948714 [ThreadId 82] INFO hls:	Using interface files cache dir: /home/cody/.cache/ghcide/main-f15759b5ccd5ca24b93acfe0be86fc6e64062e4d
2021-06-25 21:40:18.483191682 [ThreadId 82] INFO hls:	Making new HscEnv[main]
2021-06-25 21:40:18.494930499 [ThreadId 174] INFO hls:	Consulting the cradle for "src/A.hs"
Output from setting up the cradle Cradle {cradleRootDir = "/home/cody/org-roam/data/42/66517f-9ddf-40fd-b8c1-7b444364dc1b/th-pq-segfault", cradleOptsProg = CradleAction: Stack}
> Configuring GHCi with the following packages: example
> /home/cody/org-roam/data/42/66517f-9ddf-40fd-b8c1-7b444364dc1b/th-pq-segfault/.stack-work/install/x86_64-linux-nix/bf9fd1ff1ae588cb8e642dd7bbc8c5b1299cd10a51c5a3ada44fa584d7a449e0/8.10.4/pkgdb:/home/cody/.stack/snapshots/x86_64-linux-nix/bf9fd1ff1ae588cb8e642dd7bbc8c5b1299cd10a51c5a3ada44fa584d7a449e0/8.10.4/pkgdb:/nix/store/d8mbb3cjp24qi0mcwb0rkmw3jhl91rjc-ghc-8.10.4/lib/ghc-8.10.4/package.conf.d
2021-06-25 21:40:25.033914653 [ThreadId 174] INFO hls:	Using interface files cache dir: /home/cody/.cache/ghcide/main-b2b08d5ef87e8604285cfae8a7b78379a57abbe4
2021-06-25 21:40:25.034141431 [ThreadId 174] INFO hls:	Using interface files cache dir: /home/cody/.cache/ghcide/main-b2b08d5ef87e8604285cfae8a7b78379a57abbe4
2021-06-25 21:40:25.034243741 [ThreadId 174] INFO hls:	Making new HscEnv[main,main]
2021-06-25 21:40:25.297784631 [ThreadId 468] INFO hls:	finish: User TypeCheck (took 0.25s)
2021-06-25 21:40:25.298777344 [ThreadId 479] INFO hls:	finish: GetHie (took 0.00s)

Completed (3 files worked, 0 files failed)
2021-06-25 21:40:25.299049512 [ThreadId 480] INFO hls:	finish: GenerateCore (took 0.00s)
```

stack.yaml

@@ -6,3 +6,7 @@ resolver: lts-18.0
 packages:
   - .
   - ./pqexample
+
+nix:
+  enable: true
+  packages: [postgresql]