Revert "selftests: Fix O= and KBUILD_OUTPUT handling for relative paths"

This reverts commit 303e6218.

This patch breaks several CI use-cases that run kselftest builds
without using main Makefile. This fix depends on abs_objtree which
is undefined when kselftest build is invoked on selftests Makefile
without going through the main Makefile.

Revert this for now as this patch impacts selftest runs.

Fixes: 303e6218 ("selftests: Fix O= and KBUILD_OUTPUT handling for relative paths")
Reported-by: NCristian Marussi <cristian.marussi@arm.com>
Reported-by: NMichael Ellerman <mpe@ellerman.id.au>
Signed-off-by: NShuah Khan <skhan@linuxfoundation.org>

tools/testing/selftests/Makefile

@@ -86,10 +86,10 @@ override LDFLAGS =
 endif
 
 ifneq ($(O),)
-	BUILD := $(abs_objtree)
+	BUILD := $(O)
 else
 	ifneq ($(KBUILD_OUTPUT),)
-		BUILD := $(abs_objtree)/kselftest
+		BUILD := $(KBUILD_OUTPUT)/kselftest
 	else
 		BUILD := $(shell pwd)
 		DEFAULT_INSTALL_HDR_PATH := 1
@@ -102,7 +102,6 @@ include $(top_srcdir)/scripts/subarch.include
 ARCH           ?= $(SUBARCH)
 export KSFT_KHDR_INSTALL_DONE := 1
 export BUILD
-#$(info abd_objtree = $(abs_objtree) BUILD = $(BUILD))
 
 # build and run gpio when output directory is the src dir.
 # gpio has dependency on tools/gpio and builds tools/gpio