[sanitizer] Replace a local array with InternalScopedString in MaybeReexec()

[kubamracek]

Summary

MaybeReexec contains a 1024-byte long local array, which produces a warning about frame size:

.../lib/sanitizer_common/sanitizer_mac.cc:548:6: warning: stack frame size of 1132 bytes in function '__sanitizer::MaybeReexec' [-Wframe-larger-than=]

Let's replace it with InternalScopedString.

compiler-rt/trunk/lib/sanitizer_common/sanitizer_mac.cc

void MaybeReexec() {
   const char *dylib_name = StripModuleName(info.dli_fname);
   uptr dylib_name_len = internal_strlen(dylib_name);
 
   bool lib_is_in_env = dyld_insert_libraries &&
                        internal_strstr(dyld_insert_libraries, dylib_name);
   if (DyldNeedsEnvVariable() && !lib_is_in_env) {
     // DYLD_INSERT_LIBRARIES is not set or does not contain the runtime
     // library.
-    char program_name[1024];
-    uint32_t buf_size = sizeof(program_name);
-    _NSGetExecutablePath(program_name, &buf_size);
+    InternalScopedString program_name(1024);
+    uint32_t buf_size = program_name.size();
+    _NSGetExecutablePath(program_name.data(), &buf_size);
     char *new_env = const_cast<char*>(info.dli_fname);
     if (dyld_insert_libraries) {
       // Append the runtime dylib name to the existing value of
       // DYLD_INSERT_LIBRARIES.
       new_env = (char*)allocator_for_env.Allocate(old_env_len + fname_len + 2);
       internal_strncpy(new_env, dyld_insert_libraries, old_env_len);
       new_env[old_env_len] = ':';
       // Copy fname_len and add a trailing zero.
       internal_strncpy(new_env + old_env_len + 1, info.dli_fname,
                        fname_len + 1);
       // Ok to use setenv() since the wrappers don't depend on the value of
       // asan_inited.
       setenv(kDyldInsertLibraries, new_env, /*overwrite*/1);
     } else {
       // Set DYLD_INSERT_LIBRARIES equal to the runtime dylib name.
       setenv(kDyldInsertLibraries, info.dli_fname, /*overwrite*/0);
     }
     VReport(1, "exec()-ing the program with\n");
     VReport(1, "%s=%s\n", kDyldInsertLibraries, new_env);
     VReport(1, "to enable wrappers.\n");
-    execv(program_name, *_NSGetArgv());
+    execv(program_name.data(), *_NSGetArgv());
 
     // We get here only if execv() failed.
     Report("ERROR: The process is launched without DYLD_INSERT_LIBRARIES, "
            "which is required for the sanitizer to work. We tried to set the "
            "environment variable and re-execute itself, but execv() failed, "
            "possibly because of sandbox restrictions. Make sure to launch the "
            "executable with:\n%s=%s\n", kDyldInsertLibraries, new_env);
     CHECK("execv failed" && 0);