using clang to build shiboken & pyside fixes stddef.h not found

pyside now fails at 40 % on error: no member named 'DragMove' in 'QOpenGLShader

pyside2/PKGBUILD

@@ -11,15 +11,19 @@ url="https://wiki.qt.io/Qt_for_Python"
 depends=('phonon-qt5' 'qt5-3d' 'qt5-charts' 'qt5-datavis3d' 'qt5-quickcontrols2' 'qt5-script'
          'qt5-svg' 'qt5-tools' 'qt5-websockets' 'qt5-multimedia' 'qt5-remoteobjects' 'qt5-sensors'
          'qt5-serialport' 'qt5-speech' 'qtwebengine' 'shiboken2')
-makedepends=('cmake' 'python3-sphinx' 'python3-setuptools')
+makedepends=('cmake' 'python3-sphinx' 'python3-setuptools' 'clang')
 #source=("git://code.qt.io/pyside/pyside-setup.git")
 source=("https://download.qt.io/official_releases/QtForPython/${pkgname}/PySide2-${pkgver}-src/${_pkgname}-${pkgver}.tar.xz")
 sha256sums=('2ea5917652036a9007d66ba4dc0aa75f381a3a25ccf0fa70fa2d9e9c8c9dacae')
 
 prepare() {
   cd ${_pkgname}-${_pkgver}
 
+  export CC=/usr/bin/clang
+  export CXX=/usr/bin/clang++
+
   sed -i -e 's|import importlib|import importlib.machinery|' sources/shiboken2/libshiboken/embed/signature_bootstrap.py
+  sed -i -e 's|#ifndef Py_LIMITED_API|#if PY_VERSION_HEX < 0x03010000|' sources/shiboken2/libshiboken/pep384impl.cpp
 }
 
 build() {

shiboken/PKGBUILD

@@ -16,6 +16,9 @@ sha256sums=('2ea5917652036a9007d66ba4dc0aa75f381a3a25ccf0fa70fa2d9e9c8c9dacae')
 prepare() {
   cd ${_pkgname}-${_pkgver}
 
+  export CC=/usr/bin/clang
+  export CXX=/usr/bin/clang++
+
   sed -i -e 's|import importlib|import importlib.machinery|' sources/shiboken2/libshiboken/embed/signature_bootstrap.py
   sed -i -e 's|#ifndef Py_LIMITED_API|#if PY_VERSION_HEX < 0x03010000|' sources/shiboken2/libshiboken/pep384impl.cpp
 }