[X86][clang] Disable long double type for -mno-x87 option

This patch attempts to fix a compiler crash that occurs when long
double type is used with -mno-x87 compiler option.

The option disables x87 target feature, which in turn disables x87
registers, so CG cannot select them for x86_fp80 LLVM IR type. Long
double is lowered as x86_fp80 for some targets, so it leads to a
crash.

The option seems to contradict the SystemV ABI, which requires long
double to be represented as a 80-bit floating point, and it also
requires to use x87 registers.

To avoid that, `long double` type is disabled when -mno-x87 option is
set. In addition to that, `float` and `double` also use x87 registers
for return values on 32-bit x86, so they are disabled as well.

Differential Revision: https://reviews.llvm.org/D98895