[PATCH] block/export/fuse.c: fix musl build

[Fabrice Fontaine <fontaine.fabrice@gmail.com>]

Fix the following build failure on musl raised since version 6.0.0 and
https://gitlab.com/qemu-project/qemu/-/commit/4ca37a96a75aafe7a37ba51ab1912b09b7190a6b
because musl does not define FALLOC_FL_ZERO_RANGE:

../block/export/fuse.c: In function 'fuse_fallocate':
../block/export/fuse.c:563:23: error: 'FALLOC_FL_ZERO_RANGE' undeclared (first use in this function)
  563 |     } else if (mode & FALLOC_FL_ZERO_RANGE) {
      |                       ^~~~~~~~~~~~~~~~~~~~

Fixes:
 - http://autobuild.buildroot.org/results/b96e3d364fd1f8bbfb18904a742e73327d308f64

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
---
 block/export/fuse.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/block/export/fuse.c b/block/export/fuse.c
index ada9e263eb..07e31129a6 100644
--- a/block/export/fuse.c
+++ b/block/export/fuse.c
@@ -635,6 +635,7 @@ static void fuse_fallocate(fuse_req_t req, fuse_ino_t inode, int mode,
             offset += size;
             length -= size;
         } while (ret == 0 && length > 0);
+#ifdef FALLOC_FL_ZERO_RANGE
     } else if (mode & FALLOC_FL_ZERO_RANGE) {
         if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + length > blk_len) {
             /* No need for zeroes, we are going to write them ourselves */
@@ -654,6 +655,7 @@ static void fuse_fallocate(fuse_req_t req, fuse_ino_t inode, int mode,
             offset += size;
             length -= size;
         } while (ret == 0 && length > 0);
+#endif
     } else if (!mode) {
         /* We can only fallocate at the EOF with a truncate */
         if (offset < blk_len) {
-- 
2.30.2