[Sanitizer] Always provide --default-arch argument to llvm-symbolizer

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@186513 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/sanitizer_common/sanitizer_symbolizer_posix_libcdep.cc b/lib/sanitizer_common/sanitizer_symbolizer_posix_libcdep.cc
index 11bd212..b580f37 100644
--- a/lib/sanitizer_common/sanitizer_symbolizer_posix_libcdep.cc
+++ b/lib/sanitizer_common/sanitizer_symbolizer_posix_libcdep.cc
@@ -28,8 +28,10 @@
 static const char* const kSymbolizerArch = "--default-arch=x86_64";
 #elif defined(__i386__)
 static const char* const kSymbolizerArch = "--default-arch=i386";
+#elif defined(__powerpc64__)
+static const char* const kSymbolizerArch = "--default-arch=powerpc64";
 #else
-static const char* const kSymbolizerArch = "";
+static const char* const kSymbolizerArch = "--default-arch=unknown";
 #endif
 
 bool StartSymbolizerSubprocess(const char *path_to_symbolizer,