Add compiler-rt fallbacks on loongarch64-musl

Author: heiher

build.rs

@@ -514,6 +514,24 @@ mod c {
             ]);
         }
 
+        if target_arch == "loongarch64" {
+            sources.extend(&[
+                ("__extenddftf2", "extenddftf2.c"),
+                ("__netf2", "comparetf2.c"),
+                ("__addtf3", "addtf3.c"),
+                ("__multf3", "multf3.c"),
+                ("__subtf3", "subtf3.c"),
+                ("__fixtfsi", "fixtfsi.c"),
+                ("__floatsitf", "floatsitf.c"),
+                ("__fixunstfsi", "fixunstfsi.c"),
+                ("__floatunsitf", "floatunsitf.c"),
+                ("__fe_getround", "fp_mode.c"),
+                ("__divtf3", "divtf3.c"),
+                ("__trunctfdf2", "trunctfdf2.c"),
+                ("__trunctfsf2", "trunctfsf2.c"),
+            ]);
+        }
+
         // Remove the assembly implementations that won't compile for the target
         if llvm_target[0] == "thumbv6m" || llvm_target[0] == "thumbv8m.base" || target_os == "uefi"
         {