Fix kselftest builds when specifying an output dir

From: "Tyler Hicks" <[email protected]>

When attempting to build kselftests with a separate output directory, a number of the tests fail to build.

For example,

 $ rm -rf build && \
   make INSTALL_HDR_PATH=build/usr headers_install > /dev/null && \
   make O=build FORCE_TARGETS=1 TARGETS=breakpoints -C tools/testing/selftests > /dev/null
 /usr/bin/ld: cannot open output file
 build/kselftest/breakpoints/step_after_suspend_test: No such file or directory
 collect2: error: ld returned 1 exit status
 make[1]: *** [../lib.mk:146: build/kselftest/breakpoints/step_after_suspend_test] Error 1
 make: *** [Makefile:163: all] Error 2

This has already been addressed upstream with v5.18 commit 5ad51ab618de ("selftests: set the BUILD variable to absolute path"). It does not cleanly cherry pick to the linux-5.4.y branch without v5.7 commit 29e911ef7b70 ("selftests: Fix kselftest O=objdir build from cluttering top level objdir"). Commit 5ad51ab618de was written in a way that assumes that the kselftests aren't build in the top level objdir so it makes sense to bring the pre-req commit back but it does represent a slight change in behavior since the kselftests will now be built in a subdir of the specified objdir (O=).

Tyler

Muhammad Usama Anjum (1):
selftests: set the BUILD variable to absolute path

Shuah Khan (1):
selftests: Fix kselftest O=objdir build from cluttering top level
objdir

 tools/testing/selftests/Makefile | 28 ++++++++++++++++++----------
 1 file changed, 18 insertions(+), 10 deletions(-)

2.34.1