perf build: Regenerate the FEATURE_DUMP file after extra feature checks

Feature detection is done in tools/build/Makefile.feature, we may exit
there with some features not detected and then, in
tools/perf/Makefile.config try adding extra libraries to link and then
do extra feature checks to see if we now find the feature.

This is the case with the disassembler-four-args that checks if the
diassembler() function in libopcodes (binutils) has a signature with
one or with four arguments, as this is not ABI and they changed it at
some point.

This is not a problem when doing normal builds, for instance:

  $ make -C tools/perf O=/tmp/build/perf

As we don't use what is in FEATURE-DUMP at that point, but is a problem
if we pass FEATURE_DUMP=/previously-detected-features as we do in
'make -C tools/perf build-test' to reuse the feature detection in the
many build combinations we test there.

When that is done feature-disassembler-four-args will be set to 0, but
opensuse 15.1 has the four arguments function signature in
disassembler(). The build thus fails.

Fix it by rewriting the FEATURE-DUMP file at the end of
tools/perf/Makefile.config to register features we retested in that make
file.

Signed-off-by: Jiri Olsa <[email protected]>
Reported-by: Arnaldo Carvalho de Melo <[email protected]>
Tested-by: Arnaldo Carvalho de Melo <[email protected]>
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

Author: Jiri Olsa

tools/perf/Makefile.config

@@ -1224,3 +1224,9 @@ $(call detected_var,LIBDIR)
 $(call detected_var,GTK_CFLAGS)
 $(call detected_var,PERL_EMBED_CCOPTS)
 $(call detected_var,PYTHON_EMBED_CCOPTS)
+
+# re-generate FEATURE-DUMP as we may have called feature_check, found out
+# extra libraries to add to LDFLAGS of some other test and then redo those
+# tests, see the block about libbfd, disassembler-four-args, for instance.
+$(shell rm -f $(FEATURE_DUMP_FILENAME))
+$(foreach feat,$(FEATURE_TESTS),$(shell echo "$(call feature_assign,$(feat))" >> $(FEATURE_DUMP_FILENAME)))