initial SkSLJIT checkin

Docs-Preview: https://skia.org/?cl=112204
Bug: skia:
Change-Id: I10042a0200db00bd8ff8078467c409b1cf191f50
Reviewed-on: https://skia-review.googlesource.com/112204
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: Mike Klein <mtklein@chromium.org>
diff --git a/BUILD.gn b/BUILD.gn
index 7786024..1abb7e6 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -50,6 +50,9 @@
 
   skia_skqp_enable_driver_correctness_workarounds = false
   skia_skqp_global_error_tolerance = 0
+
+  skia_llvm_path = ""
+  skia_llvm_lib = "LLVM"
 }
 declare_args() {
   skia_use_dng_sdk = !is_fuchsia && skia_use_libjpeg_turbo && skia_use_zlib
@@ -171,6 +174,9 @@
     "src/xml",
     "third_party/gif",
   ]
+  if (skia_llvm_path != "") {
+    include_dirs += [ "$skia_llvm_path/include" ]
+  }
 
   defines = [ "SK_GAMMA_APPLY_TO_A8" ]
   if (is_android) {
@@ -200,6 +206,12 @@
   if (!is_official_build) {
     defines += [ "GR_TEST_UTILS=1" ]
   }
+  if (skia_llvm_path != "") {
+    defines += [ "SK_LLVM_AVAILABLE" ]
+    include_dirs += [ "$skia_llvm_path/include" ]
+    libs += [ skia_llvm_lib ]
+    lib_dirs += [ "$skia_llvm_path/lib/" ]
+  }
 }
 
 # Any code that's linked into Skia-the-library should use this config via += skia_library_configs.