Update Blimp build doc to include GN args for containerized engine.

BUG=

Review URL: https://codereview.chromium.org/1673663003

Cr-Commit-Position: refs/heads/master@{#373874}

1 files changed, 55 insertions, 15 deletions

diff --git a/blimp/docs/build.md b/blimp/docs/build.md
index 5f5a3a1..13aad6b 100644
--- a/blimp/docs/build.md
+++ b/blimp/docs/build.md
@@ -1,12 +1,17 @@
 # Using GN
-Blimp only supports building using [GN](../../tools/gn/README.md), and only
-supports building for Android and Linux. A quick overview over how to use GN can
-be found in the GN [quick start guide](../../tools/gn/docs/quick_start.md).
+Blimp only supports building using [GN](../../tools/gn/README.md). A quick
+overview over how to use GN can be found in the GN
+[quick start guide](../../tools/gn/docs/quick_start.md).
 
-## Android setup
-To setup GN, run the following command:
+There are three different build configurations depending on what you want to
+build:
+
+## Android client
+
+Create an out-directory and set the GN args:
 
 ```bash
+mkdir -p out-android/Debug
 gn args out-android/Debug
 ```
 
@@ -21,36 +26,71 @@ symbol_level = 1  # Use -g1 instead of -g2
 use_goma = true
 ```
 
-## Linux setup
-For building for Linux, you can have a side-by-side out-directory:
+To build:
 
 ```bash
-gn args out-linux/Debug
+ninja -C out-android/Debug blimp
 ```
 
-Use the same arguments as above, but remove `target_os`.
+You can also build and install incremental APK like this:
 
 ```bash
+ninja -C out-android/Debug blimp blimp_apk_incremental &&
+    out-android/Debug/bin/install_blimp_apk_incremental
+```
+
+## Engine inside a Docker container
+
+Create another out-directory and set the GN args. Note, when building to run
+inside a Docker container you'll need to set the target_os to "chromeos":
+
+```bash
+mkdir -p out-chromeos/Debug
+gn args out-chromeos/Debug
+```
+
+This will bring an editor, where you can type in the following:
+
+```bash
+target_os = "chromeos"
 is_debug = true
 is_clang = true
-is_component_build = true
 symbol_level = 1  # Use -g1 instead of -g2
 use_goma = true
 use_aura = true
 use_ozone = true
+use_alsa = false
+use_pulseaudio = false
+```
+
+To build:
+
+```bash
+ninja -C out-chromeos/Debug blimp
 ```
 
-# Building
+## "Bare" engine, no Docker container
+
+Create another out-directory and set the GN args:
 
-To build blimp, build the target ```blimp```.
+```bash
+mkdir -p out-linux/Debug
+gn args out-linux/Debug
+```
 
-## Building for Android
+This will bring an editor, where you can type in the following:
 
 ```bash
-ninja -C out-android/Debug blimp
+is_debug = true
+is_clang = true
+is_component_build = true
+symbol_level = 1  # Use -g1 instead of -g2
+use_goma = true
+use_aura = true
+use_ozone = true
 ```
 
-## Building for Linux
+To build:
 
 ```bash
 ninja -C out-linux/Debug blimp