Changed the impls argument to be an array name.

Turns out, you can't use preprocessor directives inside macro arguments.
Who'd have thought?

modules/nonfree/perf/perf_main.cpp

@@ -1,8 +1,11 @@
 #include "perf_precomp.hpp"
 #include "opencv2/ts/gpu_perf.hpp"
 
-CV_PERF_TEST_MAIN_WITH_IMPLS(nonfree, (
+static const char * impls[] = {
 #ifdef HAVE_CUDA
-                                       "cuda",
+    "cuda",
 #endif
-                                       "plain"), perf::printCudaInfo())
+    "plain"
+};
+
+CV_PERF_TEST_MAIN_WITH_IMPLS(nonfree, impls, perf::printCudaInfo())