feat: replace inline C string literals with auto-generated .wren.inc includes

Replace the manually embedded C string constants for builtin Wren modules with
a new build system that automatically generates `.wren.inc` header files from
`.wren` source files. The old `script/generate_builtins.py` is removed and
replaced by `script/wren_to_c_string.py`, which produces standalone include
files with a `PREAMBLE` containing the module name and source path. The Makefile
gains pattern rules to rebuild these `.wren.inc` files whenever the
corresponding `.wren` source changes, and the `builtin` phony target is removed
since the generation is now automatic. The `wren.mk` wildcard lists are updated
to include the new `.wren.inc` files as dependencies. The `timer.c` and
`wren_core.c` source files now `#include` their respective `.wren.inc` headers
instead of defining the string literals inline, and the `timer.wren` trailing
newline is removed.

src/module/timer.c

@@ -7,43 +7,7 @@
 #include "wren.h"
 #include "vm.h"
 
-// This is generated from builtin/module/timer.wren. Do not edit here.
-static const char* timerLibSource =
-"class Timer {\n"
-"  static sleep(milliseconds) {\n"
-"    if (!(milliseconds is Num)) Fiber.abort(\"Milliseconds must be a number.\")\n"
-"    if (milliseconds < 0) Fiber.abort(\"Milliseconds cannot be negative.\")\n"
-"    startTimer_(milliseconds, Fiber.current)\n"
-"\n"
-"    runNextScheduled_()\n"
-"  }\n"
-"\n"
-"  // TODO: Once the CLI modules are more fleshed out, find a better place to\n"
-"  // put this.\n"
-"  static schedule(callable) {\n"
-"    if (__scheduled == null) __scheduled = []\n"
-"    __scheduled.add(Fiber.new {\n"
-"      callable.call()\n"
-"      runNextScheduled_()\n"
-"    })\n"
-"  }\n"
-"\n"
-"  foreign static startTimer_(milliseconds, fiber)\n"
-"\n"
-"  // Called by native code.\n"
-"  static resumeTimer_(fiber) {\n"
-"    fiber.transfer()\n"
-"  }\n"
-"\n"
-"  static runNextScheduled_() {\n"
-"    if (__scheduled == null || __scheduled.isEmpty) {\n"
-"      Fiber.suspend()\n"
-"    } else {\n"
-"      __scheduled.removeAt(0).transfer()\n"
-"    }\n"
-"  }\n"
-"}\n"
-"\n";
+#include "timer.wren.inc"
 
 // The Wren method to call when a timer has completed.
 static WrenValue* resumeTimer;
@@ -58,7 +22,7 @@ static void timerCloseCallback(uv_handle_t* handle)
 static void timerCallback(uv_timer_t* handle)
 {
   WrenValue* fiber = (WrenValue*)handle->data;
-  
+
   // Tell libuv that we don't need the timer anymore.
   uv_close((uv_handle_t*)handle, timerCloseCallback);
 
@@ -74,24 +38,24 @@ static void startTimer(WrenVM* vm)
   {
     resumeTimer = wrenGetMethod(vm, "timer", "Timer", "resumeTimer_(_)");
   }
-  
+
   int milliseconds = (int)wrenGetArgumentDouble(vm, 1);
   WrenValue* fiber = wrenGetArgumentValue(vm, 2);
-  
+
   // Store the fiber to resume when the timer completes.
   uv_timer_t* handle = (uv_timer_t*)malloc(sizeof(uv_timer_t));
   handle->data = fiber;
-  
+
   uv_timer_init(getLoop(), handle);
   uv_timer_start(handle, timerCallback, milliseconds, 0);
 }
 
 char* timerGetSource()
 {
-  size_t length = strlen(timerLibSource);
+  size_t length = strlen(timerModuleSource);
   char* copy = (char*)malloc(length + 1);
-  strncpy(copy, timerLibSource, length + 1);
-  
+  strncpy(copy, timerModuleSource, length + 1);
+
   return copy;
 }
 
@@ -101,7 +65,7 @@ WrenForeignMethodFn timerBindForeign(
   if (strcmp(className, "Timer") != 0) return NULL;
 
   if (isStatic && strcmp(signature, "startTimer_(_,_)") == 0) return startTimer;
-  
+
   return NULL;
 }
 

src/module/timer.wren

@@ -32,4 +32,3 @@ class Timer {
     }
   }
 }
-

src/module/timer.wren.inc

@@ -0,0 +1,36 @@
+// Generated automatically from src/module/timer.wren. Do not edit.
+static const char* timerModuleSource =
+"class Timer {\n"
+"  static sleep(milliseconds) {\n"
+"    if (!(milliseconds is Num)) Fiber.abort(\"Milliseconds must be a number.\")\n"
+"    if (milliseconds < 0) Fiber.abort(\"Milliseconds cannot be negative.\")\n"
+"    startTimer_(milliseconds, Fiber.current)\n"
+"\n"
+"    runNextScheduled_()\n"
+"  }\n"
+"\n"
+"  // TODO: Once the CLI modules are more fleshed out, find a better place to\n"
+"  // put this.\n"
+"  static schedule(callable) {\n"
+"    if (__scheduled == null) __scheduled = []\n"
+"    __scheduled.add(Fiber.new {\n"
+"      callable.call()\n"
+"      runNextScheduled_()\n"
+"    })\n"
+"  }\n"
+"\n"
+"  foreign static startTimer_(milliseconds, fiber)\n"
+"\n"
+"  // Called by native code.\n"
+"  static resumeTimer_(fiber) {\n"
+"    fiber.transfer()\n"
+"  }\n"
+"\n"
+"  static runNextScheduled_() {\n"
+"    if (__scheduled == null || __scheduled.isEmpty) {\n"
+"      Fiber.suspend()\n"
+"    } else {\n"
+"      __scheduled.removeAt(0).transfer()\n"
+"    }\n"
+"  }\n"
+"}\n";