[SCons] Add option to build without threads

This is relevant for the Web platform, where builds with and without
threads are incompatible.

test/project/example.gdextension

@@ -29,8 +29,10 @@ android.debug.arm64 = "res://bin/libgdexample.android.template_debug.arm64.so"
 android.release.arm64 = "res://bin/libgdexample.android.template_release.arm64.so"
 ios.debug = "res://bin/libgdexample.ios.template_debug.xcframework"
 ios.release = "res://bin/libgdexample.ios.template_release.xcframework"
-web.debug.wasm32 = "res://bin/libgdexample.web.template_debug.wasm32.wasm"
-web.release.wasm32 = "res://bin/libgdexample.web.template_release.wasm32.wasm"
+web.debug.threads.wasm32 = "res://bin/libgdexample.web.template_debug.wasm32.wasm"
+web.release.threads.wasm32 = "res://bin/libgdexample.web.template_release.wasm32.wasm"
+web.debug.wasm32 = "res://bin/libgdexample.web.template_debug.wasm32.nothreads.wasm"
+web.release.wasm32 = "res://bin/libgdexample.web.template_release.wasm32.nothreads.wasm"
 
 [dependencies]
 ios.debug = {

tools/godotcpp.py

@@ -266,6 +266,8 @@ def options(opts, env):
         )
     )
 
+    opts.Add(BoolVariable(key="threads", help="Enable threading support", default=env.get("threads", True)))
+
     # compiledb
     opts.Add(
         BoolVariable(
@@ -393,6 +395,9 @@ def generate(env):
 
     tool.generate(env)
 
+    if env["threads"]:
+        env.Append(CPPDEFINES=["THREADS_ENABLED"])
+
     if env.use_hot_reload:
         env.Append(CPPDEFINES=["HOT_RELOAD_ENABLED"])
 
@@ -436,6 +441,8 @@ def generate(env):
     suffix += "." + env["arch"]
     if env["ios_simulator"]:
         suffix += ".simulator"
+    if not env["threads"]:
+        suffix += ".nothreads"
 
     env["suffix"] = suffix  # Exposed when included from another project
     env["OBJSUFFIX"] = suffix + env["OBJSUFFIX"]

tools/web.py

@@ -35,8 +35,9 @@ def generate(env):
     env["SHLIBSUFFIX"] = ".wasm"
 
     # Thread support (via SharedArrayBuffer).
-    env.Append(CCFLAGS=["-s", "USE_PTHREADS=1"])
-    env.Append(LINKFLAGS=["-s", "USE_PTHREADS=1"])
+    if env["threads"]:
+        env.Append(CCFLAGS=["-s", "USE_PTHREADS=1"])
+        env.Append(LINKFLAGS=["-s", "USE_PTHREADS=1"])
 
     # Build as side module (shared library).
     env.Append(CPPFLAGS=["-s", "SIDE_MODULE=1"])