Rollup merge of rust-lang#100637 - andrewpollack:fuchsia-docs-adjustments, r=tmandry

Improving Fuchsia rustc support documentation

* Adjusting `package/meta/package` to fit current schema
* Adding repository server step
* Adjusting step to give default repository
* Adding "recreate" step for easier step following

Author: matthiaskrgr

src/doc/rustc/src/platform-support/fuchsia.md

@@ -121,7 +121,10 @@ following files inside:
 
 **`package/meta/package`**
 ```json
-{"name":"hello_fuchsia","version":0}
+{
+  "name": "hello_fuchsia",
+  "version": "0"
+}
 ```
 
 The `package` file describes our package's name and version number. Every
@@ -232,10 +235,17 @@ ${SDK_PATH}/tools/${ARCH}/ffx product-bundle get workstation_eng.qemu-${ARCH}
 ${SDK_PATH}/tools/${ARCH}/ffx emu start workstation_eng.qemu-${ARCH} --headless
 ```
 
-Then, once the emulator has been started:
+Once the emulator is running, start a package repository server to serve our
+package to the emulator:
 
 ```sh
-${SDK_PATH}/tools/${ARCH}/ffx target repository register
+${SDK_PATH}/tools/${ARCH}/ffx repository server start
+```
+
+Once the repository server is up and running, register our repository:
+
+```sh
+${SDK_PATH}/tools/${ARCH}/ffx target repository register --repository hello-fuchsia
 ```
 
 And watch the logs from the emulator in a separate terminal:
@@ -253,6 +263,10 @@ ${SDK_PATH}/tools/${ARCH}/ffx component run fuchsia-pkg://hello-fuchsia/hello_fu
 On reruns of the component, the `--recreate` argument may also need to be
 passed.
 
+```sh
+${SDK_PATH}/tools/${ARCH}/ffx component run --recreate fuchsia-pkg://hello-fuchsia/hello_fuchsia#meta/hello_fuchsia.cm
+```
+
 ## Testing
 
 ### Running unit tests