Rollup merge of #147015 - Zalathar:dispose-tm, r=lqd

Use `LLVMDisposeTargetMachine`
After bumping the minimum LLVM version to 20 (#145071), we no longer need to run any custom code when disposing of a TargetMachine, so we can just use the upstream LLVM-C function.

Author: Zalathar

compiler/rustc_codegen_llvm/src/back/owned_target_machine.rs

@@ -95,8 +95,6 @@ impl Drop for OwnedTargetMachine {
 // SAFETY: constructing ensures we have a valid pointer created by
 // llvm::LLVMRustCreateTargetMachine OwnedTargetMachine is not copyable so there is no
 // double free or use after free.
-unsafe{
- llvm::LLVMRustDisposeTargetMachine(self.tm_unique.as_ptr());
-}
+unsafe{ llvm::LLVMDisposeTargetMachine(self.tm_unique)};
 }
 }

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -1053,6 +1053,8 @@ unsafe extern "C" {
 SLen:c_uint,
 ) -> MetadataKindId;
 
+pub(crate)fnLLVMDisposeTargetMachine(T: ptr::NonNull<TargetMachine>);
+
 // Create modules.
 pub(crate)fnLLVMModuleCreateWithNameInContext(
 ModuleID:*constc_char,
@@ -2499,7 +2501,6 @@ unsafe extern "C" {
 UseWasmEH:bool,
 ) -> *mutTargetMachine;
 
-pub(crate)fnLLVMRustDisposeTargetMachine(T:*mutTargetMachine);
 pub(crate)fnLLVMRustAddLibraryInfo<'a>(
 PM:&PassManager<'a>,
 M:&'aModule,

compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp

@@ -359,10 +359,6 @@ extern "C" LLVMTargetMachineRef LLVMRustCreateTargetMachine(
 returnwrap(TM);
 }
 
-extern"C"voidLLVMRustDisposeTargetMachine(LLVMTargetMachineRef TM) {
-deleteunwrap(TM);
-}
-
 // Unfortunately, the LLVM C API doesn't provide a way to create the
 // TargetLibraryInfo pass, so we use this method to do so.
 extern"C"voidLLVMRustAddLibraryInfo(LLVMPassManagerRef PMR, LLVMModuleRef M,