libxcrypt: fix cygwin build

pkgs/development/libraries/libxcrypt/default.nix

@@ -2,6 +2,7 @@
   lib,
   stdenv,
   fetchurl,
+  fetchpatch,
   perl,
   # Update the enabled crypt scheme ids in passthru when the enabled hashes change
   enableHashes ? "strong",
@@ -19,6 +20,11 @@ stdenv.mkDerivation (finalAttrs: {
     hash = "sha256-cVE6McAaQovM1TZ6Mv2V8RXW2sUPtbYMd51ceUKuwHE=";
   };
 
+  patches = [
+    # https://github.com/besser82/libxcrypt/pull/221
+    ./fix-symver-on-non-elf.patch
+  ];
+
   # this could be accomplished by updateAutotoolsGnuConfigScriptsHook, but that causes infinite recursion
   # necessary for FreeBSD code path in configure
   postPatch = ''
@@ -36,7 +42,8 @@ stdenv.mkDerivation (finalAttrs: {
     "--disable-failure-tokens"
     # required for musl, android, march=native
     "--disable-werror"
-  ];
+  ]
+  ++ lib.optional stdenv.hostPlatform.isCygwin "--disable-symvers";
 
   makeFlags =
     let
@@ -44,7 +51,7 @@ stdenv.mkDerivation (finalAttrs: {
     in
     [ ]
     # fixes: can't build x86_64-w64-mingw32 shared library unless -no-undefined is specified
-    ++ lib.optionals stdenv.hostPlatform.isWindows [ "LDFLAGS+=-no-undefined" ]
+    ++ lib.optionals stdenv.hostPlatform.isPE [ "LDFLAGS+=-no-undefined" ]
 
     # lld 17 sets `--no-undefined-version` by default and `libxcrypt`'s
     # version script unconditionally lists legacy compatibility symbols, even

pkgs/development/libraries/libxcrypt/fix-symver-on-non-elf.patch

@@ -0,0 +1,26 @@
+From 2806cc84abb7bf6aa9d9ff062944d664ab644127 Mon Sep 17 00:00:00 2001
+From: David McFarland <corngood@gmail.com>
+Date: Fri, 2 Jan 2026 13:09:02 -0400
+Subject: [PATCH] Fix compilation on Cygwin
+
+Cygwin uses COFF like Windows, so it needs the symver stub.
+---
+ lib/crypt-port.h | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/lib/crypt-port.h b/lib/crypt-port.h
+index 23c7efa..0c90ade 100644
+--- a/lib/crypt-port.h
++++ b/lib/crypt-port.h
+@@ -205,7 +205,7 @@ extern size_t strcpy_or_abort (void *dst, size_t d_size, const void *src);
+   __asm__(".globl _" extstr);                           \
+   __asm__(".set _" extstr ", _" #intname)
+ 
+-#elif defined _WIN32
++#elif defined _WIN32 || defined __CYGWIN__
+ 
+ /* .symver is only supported for ELF format, Windows uses COFF/PE */
+ # define symver_set(extstr, intname, version, mode)
+-- 
+2.51.2
+