openshadinglanguage: enable LLVM_STATIC to avoid conflicts

When OSL is included in a downstream consumer that has other
dependencies with different libllvm versions, crashes often ensue. Avoid
this by linking statically to it. This then requires libxml on Linux.

Notably, this fixes blender when built with rocmSupport, as ROCm deps
depend on a conflicting libllvm.

pkgs/by-name/op/openshadinglanguage/package.nix

@@ -32,6 +32,7 @@ stdenv.mkDerivation (finalAttrs: {
   };
 
   cmakeFlags = [
+    (lib.cmakeBool "LLVM_STATIC" true)
     (lib.cmakeBool "USE_QT" false)
 
     # Build system implies llvm-config and llvm-as are in the same directory.
@@ -60,6 +61,7 @@ stdenv.mkDerivation (finalAttrs: {
   buildInputs = [
     hexdump
     libclang
+    libxml2
     llvm
     openexr
     openimageio
@@ -68,9 +70,6 @@ stdenv.mkDerivation (finalAttrs: {
     python3Packages.pybind11
     robin-map
     zlib
-  ]
-  ++ lib.optionals stdenv.hostPlatform.isDarwin [
-    libxml2
   ];
 
   propagatedBuildInputs = [