perf build: Remove leftover feature tests for removed cxx and clang support

56b11a2126 ("perf bpf: Remove support for embedding clang for
compiling BPF events (-e foo.c)") removed the test-cxx.cpp and
test-clang.cpp sources, but left behind their entries in the feature
test FILES list, the build rules and the cxx and clang entries in
FEATURE_TESTS_EXTRA.

Since the sources no longer exist, those rules would always fail,
making the artificial feature-cxx and feature-clang results to be
perpetually disabled/absent, remove the leftover entries, making the
feature test scripts list match the available sources.

Fixes: 56b11a2126 ("perf bpf: Remove support for embedding clang for compiling BPF events (-e foo.c)")
Cc: Ian Rogers <irogers@google.com>
Assisted-by: opencode:deepseek-v4-flash-free
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

tools/build/Makefile.feature

@@ -123,9 +123,7 @@ FEATURE_TESTS_EXTRA :=                  \
          libbfd-liberty-z               \
          libopencsd                     \
          libperl                        \
-         cxx                            \
          llvm                           \
-         clang                          \
          libbpf                         \
          libpfm4                        \
          libdebuginfod			\

tools/build/feature/Makefile

@@ -55,7 +55,6 @@ FILES=                                          \
          test-bpf.bin                           \
          test-libbpf.bin                        \
          test-sdt.bin                           \
-         test-cxx.bin                           \
          test-gettid.bin			\
          test-jvmti.bin				\
          test-jvmti-cmlr.bin			\
@@ -63,7 +62,6 @@ FILES=                                          \
          test-sched_getcpu.bin			\
          test-setns.bin				\
          test-libopencsd.bin			\
-         test-clang.bin				\
          test-llvm.bin				\
          test-llvm-perf.bin   			\
          test-libaio.bin			\
@@ -335,9 +333,6 @@ $(OUTPUT)test-libbpf.bin:
 $(OUTPUT)test-sdt.bin:
 	$(BUILD)
 
-$(OUTPUT)test-cxx.bin:
-	$(BUILDXX) -std=gnu++11
-
 $(OUTPUT)test-gettid.bin:
 	$(BUILD)
 
@@ -363,15 +358,6 @@ $(OUTPUT)test-llvm-perf.bin:
 		$(shell $(LLVM_CONFIG) --system-libs)		\
 		> $(@:.bin=.make.output) 2>&1
 
-$(OUTPUT)test-clang.bin:
-	$(BUILDXX) -std=gnu++17					\
-		-I$(shell $(LLVM_CONFIG) --includedir) 		\
-		-L$(shell $(LLVM_CONFIG) --libdir)		\
-		-Wl,--start-group -lclang-cpp -Wl,--end-group	\
-		$(shell $(LLVM_CONFIG) --libs Core option)	\
-		$(shell $(LLVM_CONFIG) --system-libs)		\
-		> $(@:.bin=.make.output) 2>&1
-
 -include $(OUTPUT)*.d
 
 $(OUTPUT)test-libaio.bin: