[testsuite] Check target alias in builtin-has-attribute-3.c

[testsuite] Check target alias in builtin-has-attribute-3.c

When running test-case c-c++-common/builtin-has-attribute-3.c on nvptx, I get:
...
FAIL: c-c++-common/builtin-has-attribute-3.c  -Wc++-compat \
  (test for excess errors)
Excess errors:
src/gcc/testsuite/c-c++-common/builtin-has-attribute-3.c:33:33: error: \
  alias definitions not supported in this configuration
...

Fix this by adding -DSKIP_ALIAS to the compilation options for effective
target ! alias.

Tested on nvptx.

gcc/testsuite/ChangeLog:

	* c-c++-common/builtin-has-attribute-3.c: Compile with -DSKIP_ALIAS
	for effective target ! alias.