Disable computed goto under emscripten

Computed goto is apparently supported using the fastcomp/LLVM -> asm.js -> wasm path,
but not the upstream LLVM -> wasm path (at least not at the moment). For now simply
always disable computed goto under Emscripten.

src/flisp/Makefile

@@ -33,7 +33,10 @@ FLAGS := -I$(LLTDIR) $(JCFLAGS) $(HFILEDIRS:%=-I%) \
  -I$(LIBUV_INC) -I$(UTF8PROC_INC) -I$(build_includedir) $(LIBDIRS:%=-L%) \
  -DLIBRARY_EXPORTS -DUTF8PROC_EXPORTS
 ifneq ($(USEMSVC), 1)
-FLAGS += -Wall -Wno-strict-aliasing -DUSE_COMPUTED_GOTO -fvisibility=hidden -Wpointer-arith -Wundef
+ifneq ($(OS), emscripten)
+FLAGS += -DUSE_COMPUTED_GOTO
+endif
+FLAGS += -Wall -Wno-strict-aliasing -fvisibility=hidden -Wpointer-arith -Wundef
 FLAGS += -Wold-style-definition -Wstrict-prototypes -Wc++-compat
 endif
 

src/gc.c

@@ -1849,7 +1849,7 @@ STATIC_INLINE int gc_mark_scan_obj32(jl_ptls_t ptls, jl_gc_mark_sp_t *sp, gc_mar
  return 0;
 }
 
-#ifdef __GNUC__
+#if defined(__GNUC__) && !defined(__OS_EMSCRIPTEN__)
 # define gc_mark_laddr(name) (&&name)
 # define gc_mark_jmp(ptr) goto *(ptr)
 #else