user: add target i686

user/rcore-ulib/src/syscall.rs

@@ -10,6 +10,12 @@ fn sys_call(syscall_id: SyscallId, arg0: usize, arg1: usize, arg2: usize, arg3:
             : "{x10}" (id), "{x11}" (arg0), "{x12}" (arg1), "{x13}" (arg2), "{x14}" (arg3), "{x15}" (arg4), "{x16}" (arg5)
             : "memory"
             : "volatile");
+        #[cfg(target_arch = "x86")]
+            asm!("int 0x80"
+            : "={eax}" (ret)
+            : "{eax}" (id), "{edx}" (arg0), "{ecx}" (arg1), "{ebx}" (arg2), "{edi}" (arg3), "{esi}" (arg4)
+            : "memory"
+            : "intel" "volatile");
         #[cfg(target_arch = "x86_64")]
             asm!("int 0x40"
             : "={rax}" (ret)

user/targets/i686-rcore.json

@@ -0,0 +1,15 @@
+{
+  "arch": "x86",
+  "cpu": "pentium4",
+  "data-layout": "e-m:e-p:32:32-f64:32:64-f80:32-n8:16:32-S128",
+  "executables": true,
+  "linker-flavor": "ld.lld",
+  "linker": "rust-lld",
+  "llvm-target": "i686",
+  "max-atomic-width": 64,
+  "os": "none",
+  "target-c-int-width": "32",
+  "target-endian": "little",
+  "target-pointer-width": "32",
+  "features": "-mmx,-sse,+soft-float"
+}