[scudo] Use -fsanitize=scudo rather than --whole-archive in tests

[cryptoad]

Summary

Tests were being run by whole-linking the static library with our test binaries.
But since -fsanitize=scudo landed with rL317337, we might as well change how
the tests are compiled to use it.

The only difference will be on Android, where the clang flag links in the
dynamic library instead, but the bots are already pushing
libclang_rt.*-android.so to the device there is no additional change needed.

Tested locally, including with a standalone build, and an Android one on a O
device, and it all passes.

test/scudo/lit.cfg

 # -*- Python -*-
 
 import os
 
 # Setup config name.
 config.name = 'Scudo' + config.name_suffix
 
 # Setup source root.
 config.test_source_root = os.path.dirname(__file__)
 
-# Path to the shared & static libraries
+# Path to the shared library
 shared_libscudo = os.path.join(config.compiler_rt_libdir, "libclang_rt.scudo-%s.so" % config.target_arch)
-static_libscudo = os.path.join(config.compiler_rt_libdir, "libclang_rt.scudo-%s.a" % config.target_arch)
-static_libscudo_cxx = os.path.join(config.compiler_rt_libdir, "libclang_rt.scudo_cxx-%s.a" % config.target_arch)
-
-whole_archive = "-Wl,-whole-archive %s -Wl,-no-whole-archive " % static_libscudo
-whole_archive_cxx = "-Wl,-whole-archive %s -Wl,-no-whole-archive " % static_libscudo_cxx
 
 # Test suffixes.
 config.suffixes = ['.c', '.cc', '.cpp']
 
 # C & CXX flags.
 c_flags = ([config.target_cflags] +
            ["-pthread",
            "-fPIE",
            "-pie",
            "-O0",
            "-UNDEBUG",
            "-ldl",
            "-Wl,--gc-sections"])
 
 # Android doesn't want -lrt.
 if not config.android:
   c_flags += ["-lrt"]
 
 cxx_flags = (c_flags + config.cxx_mode_flags + ["-std=c++11"])
 
+scudo_flags = ["-fsanitize=scudo"]
+
 def build_invocation(compile_flags):                                            
   return " " + " ".join([config.clang] + compile_flags) + " "
 
 # Add clang substitutions.
 config.substitutions.append(("%clang ", build_invocation(c_flags)))
-config.substitutions.append(("%clang_scudo ", build_invocation(c_flags) + whole_archive))
-config.substitutions.append(("%clangxx_scudo ", build_invocation(cxx_flags) + whole_archive + whole_archive_cxx))
+config.substitutions.append(("%clang_scudo ", build_invocation(c_flags + scudo_flags)))
+config.substitutions.append(("%clangxx_scudo ", build_invocation(cxx_flags + scudo_flags)))
 config.substitutions.append(("%shared_libscudo", shared_libscudo))
 
 # Platform-specific default SCUDO_OPTIONS for lit tests.
 default_scudo_opts = ''
 if config.android:
   # Android defaults to abort_on_error=1, which doesn't work for us.
   default_scudo_opts = 'abort_on_error=0'