ProjectsSpec invokes `cabal run`, but Gentoo's test environment requires
GHC_PACKAGE_PATH so nested GHCi processes can see Cabal's in-place package
database.

cabal-install refuses to run when GHC_PACKAGE_PATH is set, while the
remaining doctest and spectest cases require that environment.

Skip the cabal-install integration test.
--- ../test/ProjectsSpec.hs	2026-09-12 19:10:10.119806382 +0300
+++ ../test/ProjectsSpec.hs	2026-09-12 19:10:30.311602078 +0300
@@ -24,6 +24,6 @@
         | otherwise -> describe
 
   cDescribe "T85-default-language" $ do
-    it "cabal run doctests" $ do
+    xit "cabal run doctests" $ do
       _ <- readCreateProcess (proc "cabal" ["run", "-v0", "--", "doctests", "--quiet"]) ""
       pure ()