tools build: Add feature test for abi::__cxa_demangle

cxxabi.h is part of libsdtc++ and LLVM's libcxx, providing
abi::__cxa_demangle a portable C++ demangler. Add a feature test to
detect that the function is available.

Signed-off-by: Ian Rogers <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Andres Freund <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Leo Yan <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Martin Liška <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Nathan Chancellor <[e-mail]>
Cc: Nick Desaulniers <[e-mail]>
Cc: Pavithra Gurushankar <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Quentin Monnet <[e-mail]>
Cc: Roberto Sassu <[e-mail]>
Cc: Stephane Eranian <[e-mail]>
Cc: Tiezhu Yang <[e-mail]>
Cc: Tom Rix <[e-mail]>
Cc: Yang Jihong <[e-mail]>
Cc: [e-mail]
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/build/Makefile.feature

···
          compile-32                     \
          compile-x32                    \
          cplus-demangle                 \
+         cxa-demangle                   \
          gtk2                           \
          gtk2-infobar                   \
          hello                          \

tools/build/feature/Makefile

···
          test-libbfd-liberty.bin                \
          test-libbfd-liberty-z.bin              \
          test-cplus-demangle.bin                \
+         test-cxa-demangle.bin                  \
          test-libcap.bin			\
          test-libelf.bin                        \
          test-libelf-getphdrnum.bin             \
···
 
 $(OUTPUT)test-cplus-demangle.bin:
 	$(BUILD) -liberty
+
+$(OUTPUT)test-cxa-demangle.bin:
+	$(BUILDXX)
 
 $(OUTPUT)test-backtrace.bin:
 	$(BUILD)

tools/build/feature/test-cxa-demangle.cpp

···
+// SPDX-License-Identifier: GPL-2.0
+#include <stdio.h>
+#include <stdlib.h>
+#include <cxxabi.h>
+
+int main(void)
+{
+  size_t len = 256;
+  char *output = (char*)malloc(len);
+        int status;
+
+        output = abi::__cxa_demangle("FieldName__9ClassNameFd", output, &len, &status);
+
+        printf("demangled symbol: {%s}\n", output);
+
+        return 0;
+}