On ARM, use relocation_model to detect whether r9 should be reserved

The previous approach of checking for the reserve-r9 target feature
didn't actually work because LLVM only sets this feature very late when
initializing the per-function subtarget.

compiler/rustc_target/src/asm/riscv.rs

@@ -1,5 +1,5 @@
 use super::{InlineAsmArch, InlineAsmType};
-use crate::spec::Target;
+use crate::spec::{Target, RelocModel};
 use rustc_data_structures::stable_set::FxHashSet;
 use rustc_macros::HashStable_Generic;
 use rustc_span::{sym, Symbol};
@@ -54,6 +54,7 @@ impl RiscVInlineAsmRegClass {
 
 fn not_e(
     _arch: InlineAsmArch,
+    _reloc_model: RelocModel,
     target_features: &FxHashSet<Symbol>,
     _target: &Target,
     _is_clobber: bool,