[Doc] add ccache guide in doc (vllm-project#5012)

Co-authored-by: Michael Goin <[email protected]>

docs/source/getting_started/installation.rst

@@ -56,6 +56,10 @@ You can also build and install vLLM from source:
     $ # export VLLM_INSTALL_PUNICA_KERNELS=1 # optionally build for multi-LoRA capability
     $ pip install -e .  # This may take 5-10 minutes.
 
+.. tip::
+
+    Building from source requires quite a lot compilation. If you are building from source for multiple times, it is beneficial to cache the compilation results. For example, you can install `ccache <https://github.com/ccache/ccache>`_ via either `conda install ccache` or `apt install ccache` . As long as `which ccache` command can find the `ccache` binary, it will be used automatically by the build system. After the first build, the subsequent builds will be much faster.
+
 .. tip::
     To avoid your system being overloaded, you can limit the number of compilation jobs
     to be run simultaneously, via the environment variable `MAX_JOBS`. For example: