Enable more CLIF tests on AArch64

The tests for the SIMD floating-point maximum and minimum operations
require particular care because the handling of the NaN values is
non-deterministic and may vary between platforms. There is no way to
match several NaN values in a test, so the solution is to extract the
non-deterministic test cases into a separate file that is subsequently
replicated for every backend under test, with adjustments made to the
expected results.

Copyright (c) 2021, Arm Limited.

cranelift/filetests/filetests/verifier/flags.clif

@@ -1,4 +1,5 @@
 test verifier
+target aarch64
 target i686
 
 ; Simple, correct use of CPU flags.

cranelift/filetests/filetests/verifier/scalar-to-vector.clif

@@ -1,5 +1,6 @@
 test verifier
 set enable_simd=true
+target aarch64
 target x86_64
 
 function %scalar_to_vector() {

cranelift/filetests/filetests/verifier/simd-lane-index.clif

@@ -1,5 +1,6 @@
 test verifier
 set enable_simd
+target aarch64
 target x86_64
 
 function %insertlane_i32x4() {