Fix resolving current working directory

Define `WREN_PATH_MAX` recursively using `PATH_MAX`
or use fallback.
Handle `UV_ENOBUFS` error.

Author: vladimyr

src/module/os.c

@@ -81,9 +81,18 @@ void processCwd(WrenVM* vm)
 {
   wrenEnsureSlots(vm, 1);
 
-  char buffer[WREN_PATH_MAX * 4];
-  size_t length = sizeof(buffer);
-  if (uv_cwd(buffer, &length) != 0)
+  char _buffer[PATH_MAX * 2 + 1];
+  char* buffer = _buffer;
+  size_t length = sizeof(_buffer);
+  int result = uv_cwd(buffer, &length);
+
+  if (result == UV_ENOBUFS)
+  {
+    buffer = (char *)malloc(length);
+    result = uv_cwd(buffer, &length);
+  }
+
+  if (result != 0)
   {
     wrenSetSlotString(vm, 0, "Cannot get current working directory.");
     wrenAbortFiber(vm, 0);

src/module/os.h

@@ -1,9 +1,14 @@
 #ifndef process_h
 #define process_h
 
+#include "limits.h"
 #include "wren.h"
 
-#define WREN_PATH_MAX 4096
+#ifdef PATH_MAX
+# define WREN_PATH_MAX PATH_MAX
+#else
+# define WREN_PATH_MAX 4096
+#endif
 
 // Stores the command line arguments passed to the CLI.
 void osSetArguments(int argc, const char* argv[]);