diagnostic: Disable the printer 'tests'

These just print colors to stdout, and actually do not check anything.
They're pretty, but I'm fairly confident this works now, and doesn't actually give us anything other than spam output.
Disable.

Change-Id: I6144f154345ae115f0899ca7e274fdee8947c785
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/59621
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: James Price <jrprice@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
diff --git a/src/diagnostic/printer_test.cc b/src/diagnostic/printer_test.cc
index 4808cba..ce9fd14 100644
--- a/src/diagnostic/printer_test.cc
+++ b/src/diagnostic/printer_test.cc
@@ -20,8 +20,6 @@
 namespace diag {
 namespace {
 
-using PrinterTest = testing::Test;
-
 // Actually verifying that the expected colors are printed is exceptionally
 // difficult as:
 // a) The color emission varies by OS.
@@ -32,6 +30,11 @@
 // The least we can do is to exersice the code - which is what we do here.
 // The test will print each of the colors, and can be examined with human
 // eyeballs.
+// This can be enabled or disabled with ENABLE_PRINTER_TESTS
+#define ENABLE_PRINTER_TESTS 0
+#if ENABLE_PRINTER_TESTS
+
+using PrinterTest = testing::Test;
 
 TEST_F(PrinterTest, WithColors) {
   auto printer = Printer::create(stdout, true);
@@ -89,6 +92,7 @@
   printf("\n");
 }
 
+#endif  // ENABLE_PRINTER_TESTS
 }  // namespace
 }  // namespace diag
 }  // namespace tint