ci: Patch conan recipe for Nix to be able to use on macOS (#7532)

cspell.config.yaml

@@ -233,8 +233,10 @@ words:
   - pyenv
   - pyparsing
   - qalloc
+  - qbsprofile
   - queuable
   - Raphson
+  - rcflags
   - replayer
   - rerere
   - retriable

nix/devshell.nix

@@ -1,6 +1,26 @@
 { pkgs, ... }:
 let
-  inherit (import ./packages.nix { inherit pkgs; }) commonPackages;
+  # conan is in the binary cache for Linux but not for Darwin, so on Darwin
+  # it is always built from source — and its bundled test suite is unreliable
+  # in the sandbox: `test_qbsprofile_rcflags` needs gcc (absent on Darwin, see
+  # https://github.com/NixOS/nixpkgs/pull/528995) and the patch tests are
+  # flaky from source. We only use conan as a build tool, so skip its tests on
+  # Darwin. Scoped to the dev shell (not the CI env, which builds conan on
+  # Linux from the cache). Drop once the fix reaches nixos-unstable and the
+  # lock is bumped.
+  pkgs_patched =
+    if pkgs.stdenv.isDarwin then
+      pkgs.extend (
+        final: prev: {
+          conan = prev.conan.overridePythonAttrs (_: {
+            doCheck = false;
+          });
+        }
+      )
+    else
+      pkgs;
+
+  inherit (import ./packages.nix { pkgs = pkgs_patched; }) commonPackages;
 
   # Supported compiler versions
   gccVersion = pkgs.lib.range 13 15;