[PATCH] selftests/vm: fix inability to build any vm tests

[Axel Rasmussen <axelrasmussen@google.com>]

When we stopped using KSFT_KHDR_INSTALL, a side effect is we also
changed the value of `top_srcdir`. This can be seen by looking at the
code removed by:

    49de12ba06ef ("selftests: drop KSFT_KHDR_INSTALL make target"):

(Note though that this commit didn't break this, technically the one
before it did since that's the one that stopped KSFT_KHDR_INSTALL from
being used, even though the code was still there.)

Previously lib.mk reconfigured `top_srcdir` when KSFT_KHDR_INSTALL was
being used. Now, that's no longer the case.

As a result, the path to gup_test.h in vm/Makefile was wrong, and
since it's a dependency of all of the vm binaries none of them could
be built. Instead, we'd get an "error" like:

    make[1]: *** No rule to make target '/[...]/tools/testing/selftests/vm/compaction_test', needed by 'all'.  Stop.

If we specify the path of gup_test.h relatively using selfdir instead,
now it is found correctly, and things work again.

Fixes: f2745dc0ba3d ("selftests: stop using KSFT_KHDR_INSTALL")
Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
---
 tools/testing/selftests/vm/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile
index d9fa6a9ea584..f2a12494f2d8 100644
--- a/tools/testing/selftests/vm/Makefile
+++ b/tools/testing/selftests/vm/Makefile
@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 # Makefile for vm selftests
 
-LOCAL_HDRS += $(selfdir)/vm/local_config.h $(top_srcdir)/mm/gup_test.h
+LOCAL_HDRS += $(selfdir)/vm/local_config.h $(selfdir)/../../../mm/gup_test.h
 
 include local_config.mk
 
-- 
2.37.1.595.g718a3a8f04-goog