Add -pedantic to Makefile.standalone to match production.

src/IceDefs.h

Index: src/IceDefs.h
diff --git a/src/IceDefs.h b/src/IceDefs.h
index 55e09acb8681ba438b6cf6ad214a5f101b62c0c3..d327ea63e453b110620882fb0b1ba59fd7843d4d 100644
--- a/src/IceDefs.h
+++ b/src/IceDefs.h
@@ -130,7 +130,7 @@ enum { MaxCacheLineSize = 64 };
 // Use ICE_CACHELINE_BOUNDARY to force the next field in a declaration
 // list to be aligned to the next cache line.
 #define ICE_CACHELINE_BOUNDARY                                                 \
-  alignas(MaxCacheLineSize) struct {}
+  __attribute__((aligned(MaxCacheLineSize))) int : 0
 
 // PNaCl is ILP32, so theoretically we should only need 32-bit offsets.
 typedef int32_t RelocOffsetT;