add changelog

Author: jappeace

changelog.d/pr-11718.md

@@ -0,0 +1,10 @@
+---
+synopsis: Fix --host= triple mangling during cross-compilation#11718
+packages: [cabal-install]
+prs: 11718
+---
+
+repairs (hopefully): https://github.com/haskell/cabal/issues/5887
+
+Adds an integration test which fails
+on master and now succeeds.