added skslc to BUILD.gn

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4764

Change-Id: I89330cfa4be4d43d9183a8e53b28d6c0061f33e2
Reviewed-on: https://skia-review.googlesource.com/4764
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index dab8918..13884f2 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -1356,4 +1356,17 @@
       testonly = true
     }
   }
+
+  if (skia_enable_gpu) {
+    executable("skslc") {
+      sources = [
+        "src/sksl/SkSLMain.cpp",
+      ]
+      deps = [
+        ":flags",
+        ":skia",
+      ]
+      testonly = true
+    }
+  }
 }