[compiler-rt] [builtins] Support building the 128-bit float functions on i386 (PR #122658)

[Alexander Richardson via llvm-commits]

================
@@ -28,7 +28,7 @@ char assumption_1[sizeof(long double) * CHAR_BIT == 128] = {0};
 #endif
 
 int main() {
-#if __LDBL_MANT_DIG__ == 64 && defined(__x86_64__) &&                          \
+#if __LDBL_MANT_DIG__ == 64 && (defined(__x86_64__) || defined(__i386__)) &&   \
     (defined(__FLOAT128__) || defined(__SIZEOF_FLOAT128__))
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arichardson wrote:

```suggestion
#if defined(CRT_HAS_TF_MODE) && HAS_80_BIT_LONG_DOUBLE
```

Since we include int_lib.h should be possible to simplify this

https://github.com/llvm/llvm-project/pull/122658