SCons: Add optional detect.py get_tools method to let platforms r…

…egister custom tools

This helps move this logic out of SConstruct, keeping platforms more self
contained, and helping thirdparty platforms define their own custom tools.

This logic was also unreliable (the `use_mingw` one would only work if
passed manually on the command line, not in e.g. `get_flags`).

SConstruct

@@ -86,6 +86,7 @@ if sys.stdout.isatty() and sys.platform == "win32":
 # Scan possible build platforms
 
 platform_list = []  # list of platforms
+platform_tools = {}  # SCons custom tools for each platform
 platform_opts = {}  # options for each platform
 platform_flags = {}  # flags for each platform
 platform_doc_class_path = {}
@@ -121,29 +122,25 @@ for x in sorted(glob.glob("platform/*")):
         x = x.replace("platform/", "")  # rest of world
         x = x.replace("platform\\", "")  # win32
         platform_list += [x]
+        try:  # Custom tools is optional
+            platform_tools[x] = detect.get_tools()
+        except Exception:
+            platform_tools[x] = ["default"]
         platform_opts[x] = detect.get_opts()
         platform_flags[x] = detect.get_flags()
         if isinstance(platform_flags[x], list):  # backwards compatibility
             platform_flags[x] = {flag[0]: flag[1] for flag in platform_flags[x]}
     sys.path.remove(tmppath)
     sys.modules.pop("detect")
 
-custom_tools = ["default"]
+# Define main SCons Environment
 
 platform_arg = ARGUMENTS.get("platform", ARGUMENTS.get("p", False))
-
-if platform_arg == "android":
-    custom_tools = ["clang", "clang++", "as", "ar", "link"]
-elif platform_arg == "web":
-    # Use generic POSIX build toolchain for Emscripten.
-    custom_tools = ["cc", "c++", "ar", "link", "textfile", "zip"]
-elif os.name == "nt" and methods.get_cmdline_bool("use_mingw", False):
-    custom_tools = ["mingw"]
+env = Environment(tools=platform_tools[platform_arg])
 
 # We let SCons build its default ENV as it includes OS-specific things which we don't
 # want to have to pull in manually.
 # Then we prepend PATH to make it take precedence, while preserving SCons' own entries.
-env = Environment(tools=custom_tools)
 env.PrependENVPath("PATH", os.getenv("PATH"))
 env.PrependENVPath("PKG_CONFIG_PATH", os.getenv("PKG_CONFIG_PATH"))
 if "TERM" in os.environ:  # Used for colored output.

platform/android/detect.py

@@ -19,6 +19,10 @@ def can_build():
     return os.path.exists(get_env_android_sdk_root())
 
 
+def get_tools():
+    return ["clang", "clang++", "as", "ar", "link"]
+
+
 def get_opts():
     from SCons.Variables import BoolVariable
 

platform/web/detect.py

@@ -28,6 +28,11 @@ def can_build():
     return WhereIs("emcc") is not None
 
 
+def get_tools():
+    # Use generic POSIX build toolchain for Emscripten.
+    return ["cc", "c++", "ar", "link", "textfile", "zip"]
+
+
 def get_opts():
     from SCons.Variables import BoolVariable
 

platform/windows/detect.py

@@ -155,6 +155,13 @@ def detect_build_env_arch():
     return ""
 
 
+def get_tools():
+    if os.name == "nt" and methods.get_cmdline_bool("use_mingw", False):
+        return ["mingw"]
+    else:
+        return ["default"]
+
+
 def get_opts():
     from SCons.Variables import BoolVariable, EnumVariable