librustc_back: bump ISA level of mipsel targets to mips32r2

Author: jcowgill

src/librustc_back/target/mipsel_unknown_linux_gnu.rs

@@ -25,8 +25,8 @@ pub fn target() -> TargetResult {
         linker_flavor: LinkerFlavor::Gcc,
 
         options: TargetOptions {
-            cpu: "mips32".to_string(),
-            features: "+mips32".to_string(),
+            cpu: "mips32r2".to_string(),
+            features: "+mips32r2".to_string(),
             max_atomic_width: Some(32),
 
             // see #36994

src/librustc_back/target/mipsel_unknown_linux_musl.rs

@@ -13,8 +13,8 @@ use target::{Target, TargetResult};
 
 pub fn target() -> TargetResult {
     let mut base = super::linux_musl_base::opts();
-    base.cpu = "mips32".to_string();
-    base.features = "+mips32,+soft-float".to_string();
+    base.cpu = "mips32r2".to_string();
+    base.features = "+mips32r2,+soft-float".to_string();
     base.max_atomic_width = Some(32);
     // see #36994
     base.exe_allocation_crate = None;

src/librustc_back/target/mipsel_unknown_linux_uclibc.rs

@@ -25,8 +25,8 @@ pub fn target() -> TargetResult {
         linker_flavor: LinkerFlavor::Gcc,
 
         options: TargetOptions {
-            cpu: "mips32".to_string(),
-            features: "+mips32,+soft-float".to_string(),
+            cpu: "mips32r2".to_string(),
+            features: "+mips32r2,+soft-float".to_string(),
             max_atomic_width: Some(32),
 
             // see #36994