Adapted from Debian: https://sources.debian.org/patches/sqlite3/3.32.3-1/20-hurd-locking-style.patch
Upstream status: Not upstreamed.

This patch is needed to get offloading to work.

Sqlite can use simple file locking mode, but that does not work for the Hurd;
a second sqlite process fails with a "locking protocol" error.

See also: https://bugs.debian.org/529734.

diff -purN sqlite-autoconf-3310100/sqlite3.c sqlite-autoconf-3310100-/sqlite3.c
--- sqlite-autoconf-3310100/sqlite3.c	2020-01-27 21:25:19.000000000 +0100
+++ sqlite-autoconf-3310100-/sqlite3.c	2020-07-01 11:50:13.768333806 +0200
@@ -33189,7 +33189,7 @@ SQLITE_PRIVATE const char *sqlite3Opcode
 # include <sys/mman.h>
 #endif
 
-#if SQLITE_ENABLE_LOCKING_STYLE
+#if SQLITE_ENABLE_LOCKING_STYLE || defined(__GNU__)
 /* # include <sys/ioctl.h> */
 # include <sys/file.h>
 # include <sys/param.h>
@@ -35676,7 +35676,7 @@ static int dotlockClose(sqlite3_file *id
 **
 ** Omit this section if SQLITE_ENABLE_LOCKING_STYLE is turned off
 */
-#if SQLITE_ENABLE_LOCKING_STYLE
+#if SQLITE_ENABLE_LOCKING_STYLE || defined(__GNU__)
 
 /*
 ** Retry flock() calls that fail with EINTR
@@ -38586,7 +38586,7 @@ IOMETHODS(
   0                         /* xShmMap method */
 )
 
-#if SQLITE_ENABLE_LOCKING_STYLE
+#if SQLITE_ENABLE_LOCKING_STYLE || defined(__GNU__)
 IOMETHODS(
   flockIoFinder,            /* Finder function name */
   flockIoMethods,           /* sqlite3_io_methods object name */
@@ -41142,6 +41142,8 @@ SQLITE_API int sqlite3_os_init(void){
     UNIXVFS("unix",          autolockIoFinder ),
 #elif OS_VXWORKS
     UNIXVFS("unix",          vxworksIoFinder ),
+#elif defined(__GNU__)
+    UNIXVFS("unix",          flockIoFinder ),
 #else
     UNIXVFS("unix",          posixIoFinder ),
 #endif
@@ -41151,7 +41153,7 @@ SQLITE_API int sqlite3_os_init(void){
 #if OS_VXWORKS
     UNIXVFS("unix-namedsem", semIoFinder ),
 #endif
-#if SQLITE_ENABLE_LOCKING_STYLE || OS_VXWORKS
+#if SQLITE_ENABLE_LOCKING_STYLE || OS_VXWORKS || defined(__GNU__)
     UNIXVFS("unix-posix",    posixIoFinder ),
 #endif
 #if SQLITE_ENABLE_LOCKING_STYLE