added initial GLSL support to skslc

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index 0780f1b52298c64c964ccde142a5c01902bf2b13..91c2b43ecedea5f87bb75572ae06d60c302d941f 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -459,6 +459,7 @@ test_lib("tests") {
               rebase_path("tests/PathOpsSkpClipTest.cpp"),  # alternate main
               rebase_path("tests/RTConfRegistryTest.cpp"),  # TODO: delete
               rebase_path("tests/SkSLErrorTest.cpp"),   # TODO: make work
+              rebase_path("tests/SkSLGLSLTest.cpp"),   # TODO: make work
               rebase_path("tests/SkpSkGrTest.cpp"),  # doesn't compile
               rebase_path("tests/skia_test.cpp"),  # alternate main
             ]