[libc][math] Disable FEnvSafeTest.cpp if AArch64 target has no FP support (llvm#166370)

The `FEnvSafeTest.cpp` test fails on AArch64 soft nofp configurations
because LLVM libc does not provide a floating-point environment in these
configurations.

This patch adds another preprocessor guard on `__ARM_FP` to disable the
test on those.

Author: vhscampos

libc/test/UnitTest/FEnvSafeTest.cpp

@@ -43,7 +43,8 @@ void FEnvSafeTest::set_fenv(const fenv_t &fenv) {
 
 void FEnvSafeTest::expect_fenv_eq(const fenv_t &before_fenv,
                                   const fenv_t &after_fenv) {
-#if defined(LIBC_TARGET_ARCH_IS_AARCH64) && !defined(LIBC_COMPILER_IS_MSVC)
+#if defined(LIBC_TARGET_ARCH_IS_AARCH64) && !defined(LIBC_COMPILER_IS_MSVC) && \
+    defined(__ARM_FP)
   using FPState = LIBC_NAMESPACE::fputil::FEnv::FPState;
   const FPState &before_state = reinterpret_cast<const FPState &>(before_fenv);
   const FPState &after_state = reinterpret_cast<const FPState &>(after_fenv);