glibc: Conditionally #include <linux/fs.h> to resolve fsconfig_command/mount_attr conflict with glibc 2.36

Co-authored-by: Frantisek Sumsal <frantisek@sumsal.cz>
(cherry picked from commit 1bb6ba08b1)
(cherry picked from commit a8b9c4766d)
(cherry picked from commit f048fba73f)

src/basic/linux/README

@@ -5,3 +5,4 @@ modifications are applied:
 - btrfs.h: drop '__user' attributes
 - if.h: drop '#include <linux/compiler.h>' and '__user' attributes
 - stddef.h: drop '#include <linux/compiler_types.h>'
+- guard linux/fs.h include to avoid conflict with glibc 2.36

src/basic/linux/btrfs.h

@@ -26,7 +26,9 @@ extern "C" {
 
 #include <linux/types.h>
 #include <linux/ioctl.h>
+#if WANT_LINUX_FS_H
 #include <linux/fs.h>
+#endif
 
 #define BTRFS_IOCTL_MAGIC 0x94
 #define BTRFS_VOL_NAME_MAX 255

src/basic/linux/update.sh

@@ -7,4 +7,5 @@ for i in *.h */*.h; do
     curl --fail "https://raw.githubusercontent.com/torvalds/linux/master/include/uapi/linux/$i" -o "$i"
 
     sed -r -i -e 's/__user //g' -e '/^#include <linux\/compiler(_types)?.h>/ d' "$i"
+    sed -r -i 's/^(#include <linux\/fs\.h>)/#if WANT_LINUX_FS_H\n\1\n#endif/' "$i"
 done