gdbm: fix freebsd native build

Pulls in a patch from freebsd-ports. This patch cannot be made unconditional
without a rework since it modifies the base behavior.

pkgs/by-name/gd/gdbm/freebsd-patch-src-lock-c.patch

···
+https://github.com/freebsd/freebsd-ports/blob/e198aef78afa4fd78ddc62fb5d0f7caa1b076bb0/databases/gdbm/files/patch-src_lock.c
+
+--- a/src/lock.c.orig	2025-03-06 16:24:09 UTC
++++ b/src/lock.c
+@@ -73,15 +73,10 @@ try_lock_flock (GDBM_FILE dbf, int nb)
+     {
+       return TRY_LOCK_OK;
+     }
+-  else if (errno == EWOULDBLOCK)
++  else if (errno == EWOULDBLOCK || errno == EINTR)
+     {
+       return TRY_LOCK_FAIL;
+     }
+-  else if (errno == EINTR)
+-    {
+-      errno = ETIME;
+-      return TRY_LOCK_FAIL;
+-    }
+ #endif
+   return TRY_LOCK_NEXT;
+ }
+@@ -116,7 +111,6 @@ try_lock_lockf (GDBM_FILE dbf, int nb)
+       switch (errno)
+ 	{
+ 	case EINTR:
+-	  errno = ETIME;
+ 	case EACCES:
+ 	case EAGAIN:
+ 	case EDEADLK:
+@@ -162,7 +156,6 @@ try_lock_fcntl (GDBM_FILE dbf, int nb)
+   switch (errno)
+     {
+     case EINTR:
+-      errno = ETIME;
+     case EACCES:
+     case EAGAIN:
+     case EDEADLK:

pkgs/by-name/gd/gdbm/package.nix

···
 {
   lib,
   fetchurl,
+  fetchpatch,
   stdenv,
   testers,
   updateAutotoolsGnuConfigScriptsHook,
···
     hash = "sha256-0C2zxZJu2Hf4gXuBzR+S9T73TKjG21Q/u6AnGzTzk+w=";
   };
 
-  patches = [
-    # Remove on next release.
-    ./upstream-darwin-clock-nanosleep-fix.patch
-    ./upstream-lockwait-test-fixes.patch
-    ./upstream-musl-ssize_t-fix.patch
-  ];
+  patches =
+    [
+      # Remove on next release.
+      ./upstream-darwin-clock-nanosleep-fix.patch
+      ./upstream-lockwait-test-fixes.patch
+      ./upstream-musl-ssize_t-fix.patch
+    ]
+    ++ lib.optionals stdenv.hostPlatform.isFreeBSD [
+      ./freebsd-patch-src-lock-c.patch
+    ];
 
   nativeBuildInputs = [ updateAutotoolsGnuConfigScriptsHook ];