Suggestion - colour output from SCons

It was suggested I open an issue for this. If you put `env["ENV"]["TERM"] = os.environ["TERM"]` in the SConstruct file, you can get colour output from the compiler if your terminal supports it. SCons doesn't pass terminal info to the build processes by default, cf. https://stackoverflow.com/questions/9922521/why-doesnt-clang-show-color-output-under-scons.

```diff
diff --git a/SConstruct b/SConstruct
index 27ee137..1608b91 100644
--- a/SConstruct
+++ b/SConstruct
@@ -54,6 +54,7 @@ else:
# Default tools with no platform defaults to gnu toolchain.
# We apply platform specific toolchains via our custom tools.
env = Environment(tools=["default"], PLATFORM="")
+env["ENV"]["TERM"] = os.environ["TERM"]

# Default num_jobs to local cpu count if not user specified.
# SCons has a peculiarity where user-specified options won't be overridden
```
It probably warrants a check for `if "TERM" in os.environ:`. Even if you don't really want it for building `godot-cpp` itself, I think a lot of beginners crib off or source the project's SConstruct file (as the example does, also I certainly did) and it might be nice QoL for them.

What do you think? I can open a PR if so.