anv/meson: make sure tests link with -msse2

anv/meson: make sure tests link with -msse2

Without this, I get the following error when building the tests using
meson on i686:

---8<---
In file included from ../../../mesa/src/intel/vulkan/anv_private.h:46,
                 from ../../../mesa/src/intel/vulkan/tests/state_pool_no_free.c:26:
../../../mesa/src/intel/common/gen_clflush.h: In function ‘gen_clflush_range’:
../../../mesa/src/intel/common/gen_clflush.h:37:7: error: implicit declaration of function ‘__builtin_ia32_clflush’; did you mean ‘__builtin_ia32_pause’? [-Werror=implicit-function-declaration]
       __builtin_ia32_clflush(p);
       ^~~~~~~~~~~~~~~~~~~~~~
       __builtin_ia32_pause
../../../mesa/src/intel/common/gen_clflush.h: In function ‘gen_flush_range’:
../../../mesa/src/intel/common/gen_clflush.h:45:4: error: implicit declaration of function ‘__builtin_ia32_mfence’; did you mean ‘__builtin_ia32_fnclex’? [-Werror=implicit-function-declaration]
    __builtin_ia32_mfence();
    ^~~~~~~~~~~~~~~~~~~~~
    __builtin_ia32_fnclex
---8<---

The errors are generated for each of these files:
- mesa/src/intel/vulkan/tests/state_pool_no_free.c
- mesa/src/intel/vulkan/tests/state_pool.c
- mesa/src/intel/vulkan/tests/block_pool_no_free.c
- mesa/src/intel/vulkan/tests/state_pool_free_list_only.c

This is obviously because gen_clflush.h contains code that uses
intrinsics that are only available with SSE3. Since the driver already
uses SSE3, it seems reasonable to add this to the tests as well.

Signed-off-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Eric Engeström <eric@engestrom.ch>