only use __SIZEOF_LONG_DOUBLE__ when it's 12

Author: nickdesaulniers

libc/src/__support/FPUtil/FPBits.h

@@ -127,17 +127,10 @@ template <> struct FPLayout<FPType::IEEE754_Binary128> {
 };
 
 template <> struct FPLayout<FPType::X86_Binary80> {
-// x86_64
-#if __SIZEOF_LONG_DOUBLE__ == 16
-  using StorageType = UInt128;
-// i386-linux-gnu
-#elif __SIZEOF_LONG_DOUBLE__ == 12
+#if __SIZEOF_LONG_DOUBLE__ == 12
   using StorageType = UInt<__SIZEOF_LONG_DOUBLE__ * CHAR_BIT>;
 #else
-// TODO: https://github.com/llvm/llvm-project/issues/115184
-// Android i386 uses `long double == double` i.e. `sizeof(long double) == 8`
-// https://developer.android.com/ndk/guides/abis#x86
-#error "unexpected size of long double"
+  using StorageType = UInt128;
 #endif
   LIBC_INLINE_VAR static constexpr int SIGN_LEN = 1;
   LIBC_INLINE_VAR static constexpr int EXP_LEN = 15;