Fix dlopen-mixed-c-cxx test case when libstdc++ is not available

[serge-sans-paille]

Summary

compiler-rt/test/asan/TestCases/Linux/dlopen-mixed-c-cxx.c test case requires libstdc++ to be linked and available. Make this requirement explicit.

[Hahnfeld]

For the record, I don't think this would have worked: I do have libstdc++ available on my system (I just choose SANITIZER_CXX_ABI=libcxxabi for other reasons) and passing -stdlib=libstdc++ when building the test doesn't help as I've already said in D67298. Moreover, there's nothing in the test that requires libstdc++, it just happens to pass due to many chained implications, and restricting a test without understanding the root cause is probably no good idea.

compiler-rt/test/asan/TestCases/Linux/dlopen-mixed-c-cxx.c

-// RUN: %clangxx_asan -xc++ -shared -fPIC -o %t.so - < %s
+// RUN: %clangxx_asan -xc++ -stdlib=libstdc++ -shared -fPIC -o %t.so - < %s
 // RUN: %clang_asan %s -o %t.out -ldl
 //
 // RUN: { env ASAN_OPTIONS=verbosity=1 %t.out %t.so || : ; } 2>&1 | FileCheck %s
 //
 // CHECK: {{.*}}AddressSanitizer: failed to intercept '__cxa_{{.*}}throw{{.*}}'
 //
-// REQUIRES: x86_64-target-arch && !android
+// REQUIRES: x86_64-target-arch && !android && libstdcxx
 
 #ifdef __cplusplus
 
 static void foo(void) {
   int i = 0;
   throw(i);
 }
 

compiler-rt/test/lit.common.cfg.py

 if config.android or (config.target_arch not in ['arm', 'armhf', 'aarch64']):
   config.available_features.add('stable-runtime')
 
 if config.asan_shadow_scale:
   config.available_features.add("shadow-scale-%s" % config.asan_shadow_scale)
 else:
   config.available_features.add("shadow-scale-3")
 
+if config.has_libstdcxx:
+  config.available_features.add("libstdcxx")
+
 # Propagate the LLD/LTO into the clang config option, so nothing else is needed.
 run_wrapper = []
 target_cflags = [getattr(config, 'target_cflags', None)]
 extra_cflags = []
 
 if config.use_lto and config.lto_supported:
   run_wrapper += config.lto_launch
   extra_cflags += config.lto_flags

compiler-rt/test/lit.common.configured.in

 
 if config.enable_per_target_runtime_dir:
   set_default("target_suffix", "")
 else:
   set_default("target_suffix", "-%s" % config.target_arch)
 
 set_default("have_zlib", "@HAVE_LIBZ@")
 set_default("libcxx_used", "@LLVM_LIBCXX_USED@")
+set_default("has_libstdcxx", "@COMPILER_RT_HAS_LIBSTDCXX@")
 
 # LLVM tools dir can be passed in lit parameters, so try to
 # apply substitution.
 try:
   config.llvm_tools_dir = config.llvm_tools_dir % lit_config.params
   config.clang = config.clang % lit_config.params
   config.compiler_rt_libdir = config.compiler_rt_libdir % lit_config.params
 except KeyError as e:
   key, = e.args
   lit_config.fatal("unable to find %r parameter, use '--param=%s=VALUE'" % (key, key))
 
 if not os.path.exists(config.clang):
   lit_config.fatal("Can't find compiler on path %r" % config.clang)
 
 # Setup attributes common for all compiler-rt projects.
 lit_config.load_config(config, "@COMPILER_RT_SOURCE_DIR@/test/lit.common.cfg.py")