fix: place ug dep behind not wasm32 flag (#2760)

* place `ug` behind not wasm32 attr

so that wasm32 can compile

* mv `ug` to conditional target dep

assuming every non-wasm32 user wants this

candle-core/src/cuda_backend/device.rs

@@ -51,6 +51,7 @@ impl CudaDevice {
         self.device.clone()
     }
 
+    #[cfg(not(target_arch = "wasm32"))]
     pub fn compile(
         &self,
         func_name: &'static str,

candle-core/src/custom_op.rs

@@ -386,6 +386,7 @@ pub struct UgIOp1 {
 
 impl UgIOp1 {
     #[allow(unused)]
+    #[cfg(not(target_arch = "wasm32"))]
     pub fn new(
         name: &'static str,
         kernel: ug::lang::ssa::Kernel,

candle-core/src/error.rs

@@ -172,6 +172,7 @@ pub enum Error {
     #[error("Metal error {0}")]
     Metal(#[from] MetalError),
 
+    #[cfg(not(target_arch = "wasm32"))]
     #[error(transparent)]
     Ug(#[from] ug::Error),
 

candle-core/src/metal_backend/device.rs

@@ -138,6 +138,7 @@ impl std::ops::Deref for MetalDevice {
 }
 
 impl MetalDevice {
+    #[cfg(not(target_arch = "wasm32"))]
     pub fn compile(
         &self,
         func_name: &'static str,