Library SCons boilerplate to build projects.

Works by executing project `SConstruct`s file in a cloned env (a bit
like Godot does for modules) so you don't have to worry about platform
and toolchain setup.

Convert the project test file to work as submodule, add it to CI

Run with:

```
scons build_projects=test,/path/to/other/project
```

SConstruct

@@ -144,6 +144,9 @@ opts.Add(
 )
 opts.Add(BoolVariable("generate_template_get_node", "Generate a template version of the Node class's get_node.", True))
 
+opts.Add(BoolVariable("build_library", "Build the godot-cpp library.", True))
+opts.Add("build_projects", "List of projects to build (comma-separated list of paths).", "")
+
 opts.Update(env)
 Help(opts.GenerateHelpText(env))
 
@@ -250,14 +253,13 @@ elif env["platform"] == "ios":
     env["CXX"] = compiler_path + "clang++"
     env["AR"] = compiler_path + "ar"
     env["RANLIB"] = compiler_path + "ranlib"
+    env["SHLIBSUFFIX"] = ".dylib"
 
     env.Append(CCFLAGS=["-arch", env["ios_arch"], "-isysroot", sdk_path])
     env.Append(
         LINKFLAGS=[
             "-arch",
             env["ios_arch"],
-            "-framework",
-            "Cocoa",
             "-Wl,-undefined,dynamic_lookup",
             "-isysroot",
             sdk_path,
@@ -300,8 +302,13 @@ elif env["platform"] == "windows":
 
         # Still need to use C++17.
         env.Append(CCFLAGS=["-std=c++17"])
+        # Don't want lib prefixes
+        env["IMPLIBPREFIX"] = ""
+        env["SHLIBPREFIX"] = ""
 
+        # Long line hack. Use custom spawn, quick AR append (to avoid files with the same names to override each other).
         env["SPAWN"] = mySpawn
+        env.Replace(ARFLAGS=["q"])
 
     # Native or cross-compilation using MinGW
     if host_platform == "linux" or host_platform == "freebsd" or host_platform == "osx" or env["use_mingw"]:
@@ -321,9 +328,10 @@ elif env["platform"] == "android":
         # Don't Clone the environment. Because otherwise, SCons will pick up msvc stuff.
         env = Environment(ENV=os.environ, tools=["mingw"])
         opts.Update(env)
-        # env = env.Clone(tools=['mingw'])
 
+        # Long line hack. Use custom spawn, quick AR append (to avoid files with the same names to override each other).
         env["SPAWN"] = mySpawn
+        env.Replace(ARFLAGS=["q"])
 
     # Verify NDK root
     if not "ANDROID_NDK_ROOT" in env:
@@ -389,11 +397,13 @@ elif env["platform"] == "android":
     env["CC"] = toolchain + "/bin/clang"
     env["CXX"] = toolchain + "/bin/clang++"
     env["AR"] = toolchain + "/bin/" + arch_info["tool_path"] + "-ar"
+    env["SHLIBSUFFIX"] = ".so"
 
     env.Append(
         CCFLAGS=["--target=" + arch_info["target"] + env["android_api_level"], "-march=" + arch_info["march"], "-fPIC"]
     )  # , '-fPIE', '-fno-addrsig', '-Oz'])
     env.Append(CCFLAGS=arch_info["ccflags"])
+    env.Append(LINKFLAGS=["--target=" + arch_info["target"] + env["android_api_level"], "-march=" + arch_info["march"]])
 
     if env["target"] == "debug":
         env.Append(CCFLAGS=["-Og", "-g"])
@@ -481,8 +491,16 @@ elif env["platform"] == "javascript":
 elif env["platform"] == "osx":
     arch_suffix = env["macos_arch"]
 
-library = env.StaticLibrary(
-    target="bin/" + "libgodot-cpp.{}.{}.{}{}".format(env["platform"], env["target"], arch_suffix, env["LIBSUFFIX"]),
-    source=sources,
-)
-Default(library)
+library = None
+env["OBJSUFFIX"] = ".{}.{}.{}{}".format(env["platform"], env["target"], arch_suffix, env["OBJSUFFIX"])
+library_name = "libgodot-cpp.{}.{}.{}{}".format(env["platform"], env["target"], arch_suffix, env["LIBSUFFIX"])
+
+if env["build_library"]:
+    library = env.StaticLibrary(target=env.File("bin/%s" % library_name), source=sources)
+    Default(library)
+
+env["SHLIBSUFFIX"] = "{}.{}.{}{}".format(env["platform"], env["target"], arch_suffix, env["SHLIBSUFFIX"])
+env.Append(CPPPATH=[env.Dir(f) for f in ["gen/include", "include", "godot-headers"]])
+env.Append(LIBPATH=[env.Dir("bin")])
+env.Append(LIBS=library_name)
+Return("env")