Add possibility of not compiling OGA files

The plan is to be able to compile and test NGA-only, OGA-only and both

Bug: skia:11837
Change-Id: Ib79cc2c2c437c72def8649392b345648f49300fc
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/416799
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
diff --git a/include/core/SkTypes.h b/include/core/SkTypes.h
index f30fa8a..0b09cd3 100644
--- a/include/core/SkTypes.h
+++ b/include/core/SkTypes.h
@@ -396,6 +396,14 @@
 #  define GR_TEST_UTILS 0
 #endif
 
+#ifndef GR_NGA
+#  define GR_NGA 0
+#endif
+
+#ifndef GR_OGA
+#  define GR_OGA 1
+#endif
+
 #if defined(SK_HISTOGRAM_ENUMERATION)  || \
     defined(SK_HISTOGRAM_BOOLEAN)      || \
     defined(SK_HISTOGRAM_EXACT_LINEAR) || \