meson: remove dummy_cpp

meson has gotten pretty smart about tracking C and C++ dependencies
(internal and external), and using the right linker. This wasn't always
the case and we created empty c++ files to force the use of the c++
linker. We don't need that any more.

Signed-off-by: Dylan Baker <dylan.c.baker@intel.com>
Reviewed-by: Eric Anholt <eric@anholt.net>

src/intel/vulkan/meson.build

@@ -220,7 +220,7 @@ if with_tests
       'anv_@0@'.format(t),
       executable(
         t,
-        ['tests/@0@.c'.format(t), dummy_cpp, anv_entrypoints[0]],
+        ['tests/@0@.c'.format(t), anv_entrypoints[0]],
         link_with : libvulkan_intel_test,
         dependencies : [dep_libdrm, dep_thread, dep_m, dep_valgrind],
         include_directories : [