Remove wrapper flags when clang called from intel

When using `icpx -fsycl -fsycl-host-compiler=clang++`, the inner
compiler will use the flags set in the icpx wrapper and it will break.

pkgs/intel-oneapi/patch_intel.nix

@@ -89,6 +89,10 @@ lib.makeOverridable (
 
           sed -i 's/.*isCxx=0/isCxx=1/' $out/bin/icpx
 
+          # Use this to detect when a compiler subprocess is called
+          # from icpx (--fsycl-host-compiler)
+          echo 'export NIX_CC_WRAPPER_INTEL=1' >>$out/nix-support/cc-wrapper-hook
+
           # oneMath looks for sycl libraries in bin/../lib
           ln -s ${cc}/lib $out/lib
           ln -s ${cc}/include $out/include