For libm, use a macro for aliasing symbols.

Change-Id: Ibd42ebc387c2bf3eba9aa96091770915b4b34184
diff --git a/libc/private/bionic_asm.h b/libc/private/bionic_asm.h
index d53ebba..5fca222 100644
--- a/libc/private/bionic_asm.h
+++ b/libc/private/bionic_asm.h
@@ -57,4 +57,8 @@
     ENTRY(f); \
     .hidden f \
 
+#define ALIAS_SYMBOL(alias, original) \
+    .globl alias; \
+    .equ alias, original
+
 #endif /* _PRIVATE_BIONIC_ASM_H_ */