Updating documentation for building crosvm.

Updating set_test_target to test_target.
Highlighting part that mentions running instructions inside the
container.

Bug=b:240336174
Test=None

Change-Id: I61efe14de02fe0fd98bd677a1cd8198b9085c6c7
Reviewed-on: https://chromium-review.googlesource.com/c/crosvm/crosvm/+/3788728
Reviewed-by: Dennis Kempin <denniskempin@google.com>
Tested-by: Elie Kheirallah <khei@google.com>
Commit-Queue: Elie Kheirallah <khei@google.com>
diff --git a/docs/book/src/building_crosvm.md b/docs/book/src/building_crosvm.md
index a241c60..bca19b3 100644
--- a/docs/book/src/building_crosvm.md
+++ b/docs/book/src/building_crosvm.md
@@ -73,8 +73,8 @@
 ./tools/dev_container
 ```
 
-The container image is big and may take a while to download when first used. Once started, you can
-follow all instructions in this document within the container shell.
+The container image is big and may take a while to download when first used. **Once started, you can
+follow all instructions in this document within the container shell.**
 
 Instead of using the interactive shell, commands to execute can be provided directly:
 
@@ -100,11 +100,11 @@
 You can use cargo as usual for crosvm development to `cargo build` and `cargo test` single crates
 that you are working on.
 
-If you are working on aarch64 specific code, you can use the `set_test_target` tool to instruct
-cargo to build for aarch64 and run tests on a VM:
+If you are working on aarch64 specific code, you can use the `test_target` tool to instruct cargo to
+build for aarch64 and run tests on a VM:
 
 ```sh
-./tools/set_test_target vm:aarch64 && source .envrc
+./tools/test_target set vm:aarch64 && source .envrc
 cd mycrate && cargo test
 ```