Corrected Building.md and added additional content.

Closes https://github.com/dart-lang/sdk/pull/60167

GitOrigin-RevId: 15572be15068c18e0b9787daf7fc2389ae6ee247
Change-Id: I1769a7f24dd38e1f7306372ef480af349aac30e8
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/410446
Commit-Queue: Slava Egorov <vegorov@google.com>
Reviewed-by: Slava Egorov <vegorov@google.com>

docs/Building-Dart-SDK-for-ARM-or-RISC-V.md

@@ -63,3 +63,26 @@ You can create Debian packages targeting ARM or RISC-V as follows:
 $ ./tools/linux_dist_support/create_tarball.py
 $ ./tools/linux_dist_support/create_debian_packages.py -a {ia32, x64, arm, arm64, riscv64}
 ```
+
+# Testing
+
+In addition to cross-compiling the Dart SDK, test items can also be cross-compiled. Even without the corresponding hardware, you can quickly verify if the source code modifications you made are correct. Below is a simple method for development on the riscv64 platform for your reference.
+
+Cross-compile the test items on x86_64 Linux to riscv64 and perform correctness check:
+1. Follow the steps above to cross-compile the riscv64 sdk.
+2. Cross-compile the test items by running: `./tools/build.py --mode release --arch riscv64 most run_ffi_unit_tests`.
+3. Install the necessary QEMU dependencies: `sudo apt install qemu-user qemu-user-static qemu-system`.
+4. Run the test items, e.g., `tests/lib`:
+
+```bash
+export QEMU_LD_PREFIX=/usr/riscv64-linux-gnu
+
+./tools/test.py \
+  --runtime vm \
+  --progress color \
+  --arch riscv64 \
+  --mode release \
+  --time \
+  --tasks 8 \
+  lib
+```

docs/Building.md

@@ -189,7 +189,6 @@ Dart analyzer tests example:
   --progress color \
   --arch x64 \
   --mode release \
-  --report \
   --time \
   --tasks 6 \
   language
@@ -198,13 +197,10 @@ Dart analyzer tests example:
 VM tests example:
 ```bash
 ./tools/test.py \
-  --compiler none \
   --runtime vm \
   --progress color \
   --arch x64 \
   --mode release \
-  --checked \
-  --report \
   --time \
   --tasks 6 \
   language
@@ -218,13 +214,13 @@ Dart2JS example:
   --progress color \
   --arch x64 \
   --mode release \
-  --checked \
-  --report \
   --time \
   --tasks 6 \
   language
 ```
 
+In the above examples: `--progress` is used to style the progress bar in terminal; `--time` is used to print time information; `--tasks` is used to set the number of parallel tasks; you can use `. /tools/test.py --help` for more details.
+
 ## Troubleshooting and tips for browser tests
 To debug a browser test failure, you must start a local http server to serve the test.  This is made easy with a helper script in dart/tools/testing.  The error report from test.py gives the command line to start the server in a message that reads:
 ```bash