David Sterba ebd99a6b34 btrfs: fix build when using M=fs/btrfs
There are people building the module with M= that's supposed to be used
for external modules. This got broken in e9aa7c285d20 ("btrfs: enable
W=1 checks for btrfs").

  $ make M=fs/btrfs
  scripts/Makefile.lib:10: *** Recursive variable 'KBUILD_CFLAGS' references itself (eventually).  Stop.
  make: *** [Makefile:1755: modules] Error 2

There's a difference compared to 'make fs/btrfs/btrfs.ko' which needs
to rebuild a few more things and also the dependency modules need to be
available. It could fail with eg.

  WARNING: Symbol version dump "Module.symvers" is missing.
	   Modules may not have dependencies or modversions.

In some environments it's more convenient to rebuild just the btrfs
module by M= so let's make it work.

The problem is with recursive variable evaluation in += so the
conditional C options are stored in a temporary variable to avoid the
recursion.

Signed-off-by: David Sterba <dsterba@suse.com>
2021-03-17 19:42:18 +01:00
..
2021-02-09 02:46:07 +01:00
2019-11-18 23:43:44 +01:00
2020-10-07 12:06:57 +02:00
2020-05-25 11:25:37 +02:00
2021-02-22 17:15:21 +01:00
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