Split src/opts source lists out of opts.gyp.

This should make it easier to keep our opts.gyp in sync with Chrome's GYP and GN.

BUG=skia:

Landing this without review as a mega-tryjob.
TBR=reed@google.com

Committed: https://skia.googlesource.com/skia/+/c98fe3aa4f8c97c462c0eb6d9106fc37e48d7f82

Review URL: https://codereview.chromium.org/870353003
diff --git a/gyp/skia_lib.gyp b/gyp/skia_lib.gyp
index 6bf6bc0..9f61871 100644
--- a/gyp/skia_lib.gyp
+++ b/gyp/skia_lib.gyp
@@ -15,7 +15,7 @@
       [ 'skia_arch_type == "x86" and skia_os != "android"', {
         'component_libs': [
           'opts.gyp:opts_ssse3',
-          'opts.gyp:opts_sse4',
+          'opts.gyp:opts_sse41',
         ],
       }],
       [ 'arm_neon == 1', {