qt53-qtbase: fix 32bit build

build with 64 bit compatible structures even when building 32 bit
this is how qt53 is written
placed in clang-mac.conf so this will be available for +universal as well
this does not change 64bit bit builds, so no revbump required

closes: https://trac.macports.org/ticket/58390

aqua/qt53/files/patch-mkspecs.diff

@@ -2,16 +2,17 @@ diff --git mkspecs/common/clang-mac.conf mkspecs/common/clang-mac.conf
 index 3280274f..38f0bd34 100644
 --- mkspecs/common/clang-mac.conf
 +++ mkspecs/common/clang-mac.conf
-@@ -6,5 +6,7 @@ QMAKE_OBJCXXFLAGS_USE_PRECOMPILE = $$QMAKE_CFLAGS_USE_PRECOMPILE
+@@ -6,5 +6,8 @@ QMAKE_OBJCXXFLAGS_USE_PRECOMPILE = $$QMAKE_CFLAGS_USE_PRECOMPILE
 
  QMAKE_XCODE_GCC_VERSION = com.apple.compilers.llvm.clang.1_0
 
 -QMAKE_CXXFLAGS_CXX11 += -stdlib=libc++
 -QMAKE_LFLAGS_CXX11   += -stdlib=libc++
 +QMAKE_CXXFLAGS_CXX11 += -stdlib=__MACPORTS_CXX_STDLIB__
 +QMAKE_LFLAGS_CXX11   += -stdlib=__MACPORTS_CXX_STDLIB__
-+QMAKE_CXXFLAGS += -stdlib=__MACPORTS_CXX_STDLIB__
-+QMAKE_LFLAGS   += -stdlib=__MACPORTS_CXX_STDLIB__
++QMAKE_CXXFLAGS       += -stdlib=__MACPORTS_CXX_STDLIB__
++QMAKE_LFLAGS         += -stdlib=__MACPORTS_CXX_STDLIB__
++DEFINES              +=  NS_BUILD_32_LIKE_64
 diff --git mkspecs/common/clang.conf mkspecs/common/clang.conf
 index d58b44b2..2ad29ef3 100644
 --- mkspecs/common/clang.conf