For libm, use a macro for aliasing symbols.

Change-Id: Ibd42ebc387c2bf3eba9aa96091770915b4b34184
diff --git a/libm/x86/trunc.S b/libm/x86/trunc.S
index 2f21e88..da9d5fb 100644
--- a/libm/x86/trunc.S
+++ b/libm/x86/trunc.S
@@ -40,5 +40,4 @@
 	ret
 END(trunc)
 
-.globl truncl;
-.equ truncl, trunc;
+ALIAS_SYMBOL(truncl, trunc);