Linux bugfixes for globcasedetect (re: 7193457) (att#240)

src/lib/libast/features/lib,
src/lib/libast/path/pathicase.c:
- FAT32 file systems on Linux don't support FS_CASEFOLD_FL, which
  caused globbing to break. Reproducer using a UEFI boot partition:
      $ echo /boot/eF*
      /boot/eF*
  This is fixed by checking for FAT attributes with ioctl, then
  checking for FS_CASEFOLD_FL if that fails.
- The check for FS_CASEFOLD_FL didn't work correctly; I still wasn't
  able to get --globcasedetect to work on a case-insensitive ext4
  folder. Fix that by adding missing parentheses.

src/lib/libast/features/lib

@@ -4,7 +4,7 @@ cmd	universe
 
 hdr	dirent,direntry,filio,fmtmsg,fnmatch,jioctl,libgen,limits
 hdr	locale,ndir,nl_types,process,spawn,syslog,utime,vfork
-hdr	linux/fs,sys/ioctl
+hdr	linux/fs,linux/msdos_fs,sys/ioctl
 hdr	wchar note{ <wchar.h> and isw*() really work }end execute{
 	#include <wchar.h>
 	int

src/lib/libast/path/pathicase.c

@@ -17,11 +17,23 @@
 #include <ast.h>
 #include <error.h>
 
-#if _hdr_linux_fs && _hdr_sys_ioctl
+#if _hdr_linux_fs
 #include <linux/fs.h>
+#endif
+#if _hdr_linux_msdos_fs
+#include <linux/msdos_fs.h>
+#endif
+#if _hdr_sys_ioctl
 #include <sys/ioctl.h>
 #endif
 
+#if _hdr_sys_ioctl && _hdr_linux_fs && defined(FS_IOC_GETFLAGS) && defined(FS_CASEFOLD_FL)
+#define _linux_casefold	1
+#endif
+#if _hdr_sys_ioctl && _hdr_linux_msdos_fs && defined(FAT_IOCTL_GET_ATTRIBUTES)
+#define _linux_fatfs	1
+#endif
+
 /*
  * Return 1 if the given path is on a case insensitive file system, 0 if not, -1 on error.
  */
@@ -40,14 +52,23 @@ pathicase(const char *path)
 	/* Cygwin */
 	long r = pathconf(path, _PC_CASE_INSENSITIVE);
 	return r < 0L ? -1 : r > 0L;
-#elif _hdr_linux_fs && _hdr_sys_ioctl && defined(FS_IOC_GETFLAGS) && defined(FS_CASEFOLD_FL)
-	/* Linux 5.2+ */
+#elif _linux_fatfs
+	/* Linux */
 	int attr = 0, fd, r;
 	if ((fd = open(path, O_RDONLY|O_NONBLOCK)) < 0)
 		return -1;
-	r = ioctl(fd, FS_IOC_GETFLAGS, &attr);
+	r = ioctl(fd, FAT_IOCTL_GET_ATTRIBUTES, &attr);
+#   if _linux_casefold
+	/* Linux 5.2+ */
+	if (r < 0 && errno == ENOTTY)	/* if it's not VFAT/FAT32...*/
+	{
+		r = ioctl(fd, FS_IOC_GETFLAGS, &attr);
+		close(fd);
+		return r < 0 ? -1 : (attr & FS_CASEFOLD_FL) != 0;
+	}
+#   endif /* _linux_casefold */
 	close(fd);
-	return r < 0 ? -1 : attr & FS_CASEFOLD_FL != 0;
+	return r < 0 ? (errno != ENOTTY ? -1 : 0) : 1;
 #elif _WINIX || __APPLE__
 	/* Windows or Mac without pathconf probe: assume case insensitive */
 	return 1;