Don't use an STL for libm.

The default is none right now, but this will be needed when the
default becomes libc++.

Change-Id: Ib022adac2b9dc08fbfae830908128043cfffb91e
diff --git a/libm/Android.mk b/libm/Android.mk
index 69a17a1..0f63d7b 100644
--- a/libm/Android.mk
+++ b/libm/Android.mk
@@ -295,6 +295,7 @@
 LOCAL_C_INCLUDES_mips64 := $(libm_ld_includes)
 LOCAL_SRC_FILES_mips64 := mips/fenv.c $(libm_ld_src_files)
 
+LOCAL_CXX_STL := none
 include $(BUILD_STATIC_LIBRARY)
 
 #
@@ -312,6 +313,8 @@
 
 LOCAL_NATIVE_COVERAGE := $(bionic_coverage)
 
+LOCAL_CXX_STL := none
+
 # We'd really like to do this for all architectures, but since this wasn't done
 # before, these symbols must continue to be exported on LP32 for binary
 # compatibility.