Cygwin build fixes (#1332)

* Workaround for Cygwin build

On cygwin, `__STRICT_ANSI__` does not show POSIX definitions. Use
gnu++11 language instead.

* wasm-decompile: Silence -Wsign-compare

Silence -Wsign-compare warning, by using unsigned literal one.

* wasm-objdump: Fix 4294967296 output on disasm

Use `%u` instead of `%lu` as we use `uint32_t` here.

CMakeLists.txt

@@ -118,7 +118,15 @@ else ()
     -Wuninitialized
   )
 
-  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -Wold-style-cast")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wold-style-cast")
+
+  if(NOT CYGWIN)
+      set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
+  else()
+      # On Cygwin, POSIX extensions are not visible with std=c++11 
+      # because it defines __STRICT_ANSI__.
+      set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=gnu++11")
+  endif()
 
   if (WERROR)
     add_definitions(-Werror)

src/binary-reader-objdump.cc

@@ -598,7 +598,7 @@ Result BinaryReaderObjdumpDisassemble::OnOpcodeUint32(uint32_t value) {
 Result BinaryReaderObjdumpDisassemble::OnOpcodeUint32Uint32(uint32_t value,
                                                             uint32_t value2) {
   Offset immediate_len = state->offset - current_opcode_offset;
-  LogOpcode(immediate_len, "%lu %lu", value, value2);
+  LogOpcode(immediate_len, "%u %u", value, value2);
   return Result::Ok;
 }
 

src/decompiler.cc

@@ -302,7 +302,7 @@ struct Decompiler {
         if (se.opcode == Opcode::I32Shl &&
             const_exp.etype == ExprType::Const) {
           auto& ce = *cast<ConstExpr>(const_exp.e);
-          if (ce.const_.type == Type::I32 && (1 << ce.const_.u32) == align) {
+          if (ce.const_.type == Type::I32 && (1U << ce.const_.u32) == align) {
             // Pfew, case detected :( Lets re-write this in Haskell.
             // TODO: we're decompiling these twice.
             // The thing to the left of << is going to be part of the index.