runtime: small Native Client fixes

cgocall.c: define the CBARGS macro for GOARCH_amd64p32. I don't think the value of this macro will ever be used under nacl/amd64p32 but it is required to compile even if cgo is not used.

hashmap.goc: amd64p32 uses 32bit words.

LGTM=iant
R=rsc, iant
CC=golang-codereviews
https://golang.org/cl/69960044

src/pkg/runtime/cgocall.c

@@ -223,6 +223,12 @@ struct CallbackArgs
 #define CBARGS (CallbackArgs*)((byte*)m->g0->sched.sp+2*sizeof(void*))
 #endif
 
+// There is no cgo support for nacl/amd64p32 but we need to have something here 
+// so use the amd64 value as a placeholder.
+#ifdef GOARCH_amd64p32
+#define CBARGS (CallbackArgs*)((byte*)m->g0->sched.sp+2*sizeof(void*))
+#endif
+
 // On 386, stack frame is three words, plus caller PC.
 #ifdef GOARCH_386
 #define CBARGS (CallbackArgs*)((byte*)m->g0->sched.sp+4*sizeof(void*))

src/pkg/runtime/hashmap.goc

@@ -448,6 +448,9 @@ hash_lookup(MapType *t, Hmap *h, byte **keyp)
 #ifdef GOARCH_amd64
 #define CHECKTYPE uint64
 #endif
+#ifdef GOARCH_amd64p32
+#define CHECKTYPE uint32
+#endif
 #ifdef GOARCH_386
 #define CHECKTYPE uint32
 #endif