From 1a9ad281e48f732615d60873f993eda093adfa44 Mon Sep 17 00:00:00 2001
From: David McFarland <corngood@gmail.com>
Date: Sat, 13 Sep 2025 18:05:59 -0300
Subject: [PATCH] build-support/lib/cmake: fix CMAKE_SYSTEM_NAME in cygwin
 cross

---
 pkgs/build-support/lib/cmake.nix | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/pkgs/build-support/lib/cmake.nix b/pkgs/build-support/lib/cmake.nix
index 796f69235475..f495f3d1d6bf 100644
--- a/pkgs/build-support/lib/cmake.nix
+++ b/pkgs/build-support/lib/cmake.nix
@@ -12,7 +12,9 @@ let
     [
       "-DCMAKE_SYSTEM_NAME=${
         findFirst isString "Generic" (
-          optional (!stdenv.hostPlatform.isRedox) stdenv.hostPlatform.uname.system
+          # uname -s is CYGWIN_NT[...] on cygwin, but cmake expects CYGWIN
+          optional (stdenv.hostPlatform.isCygwin) "CYGWIN"
+          ++ optional (!stdenv.hostPlatform.isRedox) stdenv.hostPlatform.uname.system
         )
       }"
     ]