Fix SkSL test compilation on Windows.

The command-line length limit on Windows is very low (~8000 characters)
so it's infeasible to pass a large number of test files directly on the
command line. Fortunately, GN includes a built-in workaround.

Change-Id: I087fc00f11d81d84f677c2833406b4a6164ea6b3
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/360716
Commit-Queue: John Stiles <johnstiles@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>

BUILD.gn

@@ -710,10 +710,12 @@ if (skia_compile_sksl_tests) {
       ]
       sources = []
       outputs = []
+      response_file_contents = []
       args = [
         rebase_path(skslc_path),
         invoker.lang,
         invoker.settings,
+        "{{response_file_name}}",
       ]
 
       testsDir = get_path_info("tests", "abspath")
@@ -726,10 +728,10 @@ if (skia_compile_sksl_tests) {
         dir = get_path_info(dst, "dir")
         name = get_path_info(dst, "name")
         ext = get_path_info(dst, "extension")
-        args += rebase_path([
-                              src,
-                              dir,
-                            ])
+        response_file_contents += rebase_path([
+                                                src,
+                                                dir,
+                                              ])
         sources += [ src ]
 
         foreach(outExtension, invoker.outExtensions) {

gn/compile_sksl_tests.py

@@ -6,15 +6,18 @@
 # found in the LICENSE file.
 
 import os
+import shlex
 import subprocess
 import sys
 import tempfile
 
+batchCompile = True
+
 skslc = sys.argv[1]
 lang = sys.argv[2]
 settings = sys.argv[3]
-inputs = sys.argv[4:]
-batchCompile = True
+with open(sys.argv[4], 'r') as reader:
+    inputs = shlex.split(reader.read())
 
 def pairwise(iterable):
     # Iterate over an array pairwise (two elements at a time).