Remove obsolete __clang__ check (and `-D`).

We've been all-clang, all the time for years now.

Change-Id: I1296a762335e614529ffd92c2a6b26f87861361b
diff --git a/tests/Android.bp b/tests/Android.bp
index d2a3110..cfaeced 100644
--- a/tests/Android.bp
+++ b/tests/Android.bp
@@ -719,11 +719,6 @@
     ],
     srcs: ["clang_fortify_tests.cpp"],
     tidy: false,
-    target: {
-        host: {
-            cflags: ["-D__clang__"],
-        },
-    },
 }
 
 cc_test_library {
diff --git a/tests/clang_fortify_tests.cpp b/tests/clang_fortify_tests.cpp
index f4ef4ac..f08fd1f 100644
--- a/tests/clang_fortify_tests.cpp
+++ b/tests/clang_fortify_tests.cpp
@@ -14,10 +14,6 @@
  * limitations under the License.
  */
 
-#ifndef __clang__
-#error "Non-clang isn't supported"
-#endif
-
 //
 // Clang compile-time and run-time tests for Bionic's FORTIFY.
 //