Fix compile on some platforms

Controlling the type of getmntinfo's param was decided by
whether or not we had the statvfs type avaliable. But getmntinfo uses
statfs regardless of this except on netbsd where it uses statvfs.

Add a check to detect which type our version of the function uses.

meson.build

@@ -182,7 +182,22 @@ foreach type : [
   endif
 endforeach
 
-if conf.has('HAVE_STRUCT_STATVFS_F_FLAG')
+
+if conf.has('HAVE_GETMNTINFO')
+  if cc.compiles('''
+      #include <sys/types.h>
+      #include <sys/statvfs.h>
+
+      void func() {
+        struct statvfs *buf;
+        getmntinfo(&buf, 0);
+      }
+      ''')
+      conf.set('FSSTATSTYPE', 'struct statvfs')
+  else
+      conf.set('FSSTATSTYPE', 'struct statfs')
+  endif
+elif conf.has('HAVE_STRUCT_STATVFS_F_FLAG')
   conf.set('FSSTATSTYPE', 'struct statvfs')
 elif conf.has('HAVE_STRUCT_STATFS_F_FLAGS')
   conf.set('FSSTATSTYPE', 'struct statfs')