Notes on how to build SKQP for Fuchsia.

Change-Id: I85477806b151773bc715f31bcdb05554107cc6b4
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/257700
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>

Author: rosasco-wk

build/fuchsia/skqp/README.md

@@ -1,4 +1,21 @@
-# CIPD Package Creation and Upload Procedure
+# Building SKQP for Fuchsia
+Using an arm64 device as an example, to build skqp for Fuchsia:
+```
+gn gen out/fuchsia-arm64 --args="is_official_build=false is_debug=false skia_update_fuchsia_sdk=true target_cpu=\"arm64\" target_os=\"fuchsia\" using_fuchsia_sdk=true skia_tools_require_resources=true skia_skqp_global_error_tolerance=8"
+```
+
+The effect of `skia_update_fuchsia_sdk=true` is that it will download both the Fuchsia SDK and a compatible clang for building SKQP as part of the `gn gen ...` step above.
+
+Next step, compile skqp for Fuchsia:
+```
+autoninja -C out/fuchsia-arm64 ":skqp_repo"
+```
+
+The effect of this build will be to produce a Fuchsia package repository named `skqp_repo` in the `out` directory of the build.  `skqp_repo` can then be served to a Fuchsia device using `//fuchsia/sdk/tools/pm serve -repo skqp_repo` (where // is the skia build root).
+
+See [install fuchsia packages](https://fuchsia.dev/fuchsia-src/development/sdk/documentation/packages#install-package) for more on serving packages to Fuchsia devices.
+
+# Fuchsia CIPD Package Creation and Upload Procedure
 These steps assume the creation of the arm64 CIPD package as an example.  Because the package requires a path from the output directory of the build, the `gn gen` arguments must match the prescribed path declared in `cipd_arm64.yaml` in order for this CIPD package creation and upload to succeed.
 
 ## Create CIPD Package