Add back eh_unwind_resume lang item for bootstrap

Author: Amanieu

src/libpanic_abort/lib.rs

@@ -116,6 +116,16 @@ pub mod personalities {
         1 // `ExceptionContinueSearch`
     }
 
+    // Similar to above, this corresponds to the `eh_unwind_resume` lang item
+    // that's only used on Windows currently.
+    //
+    // Note that we don't execute landing pads, so this is never called, so it's
+    // body is empty.
+    #[no_mangle]
+    #[cfg(bootstrap)]
+    #[cfg(all(target_os = "windows", target_env = "gnu"))]
+    pub extern fn rust_eh_unwind_resume() {}
+
     // These two are called by our startup objects on i686-pc-windows-gnu, but
     // they don't need to do anything so the bodies are nops.
     #[no_mangle]

src/libpanic_unwind/gcc.rs

@@ -302,6 +302,15 @@ unsafe fn find_eh_action(context: *mut uw::_Unwind_Context, foreign_exception: b
     eh::find_eh_action(lsda, &eh_context, foreign_exception)
 }
 
+// See docs in the `unwind` module.
+#[cfg(bootstrap)]
+#[cfg(all(target_os="windows", any(target_arch = "x86", target_arch = "x86_64"), target_env="gnu"))]
+#[lang = "eh_unwind_resume"]
+#[unwind(allowed)]
+unsafe extern "C" fn rust_eh_unwind_resume(panic_ctx: *mut u8) -> ! {
+    uw::_Unwind_Resume(panic_ctx as *mut uw::_Unwind_Exception);
+}
+
 // Frame unwind info registration
 //
 // Each module's image contains a frame unwind info section (usually