liteparse: carry forward riscv64 patches to 2.16.0

Nightly version bump omitted the patches/liteparse/<version> directory for
2.16.0, so the pdfium job's unconditional `git apply .../*.patch` step
failed with "No such file or directory" before any build/test ran.
Copied forward the same patch set from 2.15.1; it still applies to the
chromium/8058 skia/BUILD.gn that 2.16.0 pins.

Author: luhenry

patches/liteparse/2.16.0/0001-skia-accept-riscv64-target-cpu.patch

@@ -0,0 +1,19 @@
+Upstream-Status: To upstream [not yet submitted; pdfium main's skia/BUILD.gn still lacks the riscv64 branch Chromium's copy has]
+
+PDFium's skia/BUILD.gn asserts on every target CPU its skia_opts chain does not
+name, so `gn gen` fails for target_cpu = "riscv64" even with pdf_use_skia=false:
+the root BUILD.gn's gn_check group depends on //skia whenever checkout_skia is set,
+which it is for checkout_configuration=small. Chromium's own skia/BUILD.gn already
+carries this empty riscv64 branch (Skia's portable code path needs no extra flags).
+diff --git a/skia/BUILD.gn b/skia/BUILD.gn
+--- a/skia/BUILD.gn
++++ b/skia/BUILD.gn
+@@ -560,6 +560,8 @@ skia_source_set("skia_opts") {
+     # Conditional and empty body needed to avoid assert below
+   } else if (current_cpu == "mipsel" || current_cpu == "mips64el") {
+     cflags += [ "-fomit-frame-pointer" ]
++  } else if (current_cpu == "riscv64") {
++    # Conditional and empty body needed to avoid assert() below.
+   } else {
+     assert(false, "Unsupported target CPU " + current_cpu)
+   }