unittests/ASM: Adds unittest for implicit flag clobber for #3254

It looks like currently FEX has a bug around implicit flag clobbering
with this pull request where an IR operation that implicitly clobbers
flags isn't correctly saving the NZCV flags before doing the operation.

Adds a unit test that specifically captures this issue. RAX will be 1 or
0 depending on if the flags are clobbered incorrectly or not.

unittests/ASM/FEX_bugs/nzcv_implicit_clobber.asm

@@ -0,0 +1,40 @@
+%ifdef CONFIG
+{
+  "RegData": {
+    "RAX": "0",
+    "XMM0": ["0", "0"]
+  }
+}
+%endif
+
+; FEX has a bug with NZCV host flag usage that IR operations that implicitly clobber flags might not save emulated eflags correctly in all instances.
+; This tests one particular instance of `ImplicitFlagClobber`.
+movaps xmm0, [rel .data]
+
+; Calculate ZF up-front
+mov eax, 1
+add eax, eax
+
+; This jump is necessary to break visibility.
+jmp .begin
+.begin:
+
+; minss turns in to VFMinScalarInsert which implicitly clobbers Arm64 flags.
+; Potentially any instruction that uses an IR operation that uses `ImplicitFlagClobber` would break.
+minss   xmm0, xmm0
+
+; Ensure the flags calculated by the `add eax, eax` are consumed.
+; ZF should be unset from `add 1, 1`.
+; If minss clobbers Arm64 host flags then the `fcmp` that Arm64 uses will overwrite nzcv, thus setting the ZF flag.
+; This is since `fcmp #0, #0` will set nzcv to `0110`.
+jnz .next
+mov eax, 1
+hlt
+
+.next:
+mov eax, 0
+hlt
+
+align 16
+.data:
+dd 0, 0, 0, 0