Add stm32f429i to the default build target

About time.

Change-Id: Iab389228bce18c0fc17d5ba4b24fe4ca4b0ad790
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/18356
Reviewed-by: Ewout van Bekkum <ewout@google.com>
Reviewed-by: Keir Mierle <keir@google.com>
Commit-Queue: Armando Montanez <amontanez@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index 381f3cc..0a874f9 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -42,6 +42,7 @@
   deps = [
     ":docs",
     ":host",
+    ":stm32f429i",
   ]
 }
 
diff --git a/docs/getting_started.md b/docs/getting_started.md
index 5aa6357..59e17de 100644
--- a/docs/getting_started.md
+++ b/docs/getting_started.md
@@ -43,7 +43,7 @@
 (4) Start the watcher. The watcher will invoke Ninja to build all the targets
 
 ```bash
-$ pw watch out default stm32f429i
+$ pw watch out default
 
  ▒█████▄   █▓  ▄███▒  ▒█    ▒█ ░▓████▒ ░▓████▒ ▒▓████▄
   ▒█░  █░ ░█▒ ██▒ ▀█▒ ▒█░ █ ▒█  ▒█   ▀  ▒█   ▀  ▒█  ▀█▌
@@ -52,7 +52,7 @@
   ▒█      ░█░ ░▓███▀   ▒█▓▀▓█░ ░▓████▒ ░▓████▒ ▒▓████▀
 
 20200707 17:24:06 INF Starting Pigweed build watcher
-20200707 17:24:06 INF Will build [1/1]: out default stm32f429i
+20200707 17:24:06 INF Will build [1/1]: out default
 20200707 17:24:06 INF Attaching filesystem watcher to $HOME/wrk/pigweed/...
 20200707 17:24:06 INF Triggering initial build...
 ...
@@ -232,32 +232,24 @@
 
 ## Building for a Device
 
-As mentioned previously, Pigweed builds for host by default. In the context of
-Pigweed, a Pigweed "target" is a build configuration that includes a toolchain,
-default library configurations, and more to result in binaries that run
-natively on the target.
+A Pigweed "target" is a build configuration that includes a toolchain, default
+library configurations, and more to result in binaries that run natively on the
+target. With the default build invocation, you're already building for a device
+target (the STMicroelectronics STM32F429I-DISC1) in parallel with the host
+build!
 
-Switch to the window running `pw_watch`, and quit using `ctrl+c`. To get
-`pw_watch` to build the new STM32F429I-DISC1 target, re-launch by specifying
-which Ninja targets to build:
+If you want to build JUST for the device, you can kick of watch with:
 
 ```bash
-$ pw watch out default stm32f429i
+$ pw watch out stm32f429i
 ```
 
 This is equivalent to the following Ninja invocation:
 
 ```bash
-$ ninja -C out default stm32f429i
+$ ninja -C out stm32f429i
 ```
 
-Or since the "default" target builds host and docs,
-
-```bash
-$ ninja -C out host docs stm32f429i
-```
-
-Now `pw_watch` is building for host and a device!
 
 ## Running Tests on a Device