[ruby/prism] Add explicit check for PRISM_HAS_NO_FILESYSTEM

https://github.com/ruby/prism/commit/89c22f0e6c

prism/defines.h

@@ -118,6 +118,15 @@
 #   endif
 #endif
 
+/**
+ * If PRISM_HAS_NO_FILESYSTEM is defined, then we want to exclude all filesystem
+ * related code from the library. All filesystem related code should be guarded
+ * by PRISM_HAS_FILESYSTEM.
+ */
+#ifndef PRISM_HAS_NO_FILESYSTEM
+#   define PRISM_HAS_FILESYSTEM
+#endif
+
 /**
  * isinf on Windows is defined as accepting a float, but on POSIX systems it
  * accepts a float, a double, or a long double. We want to mirror this behavior

prism/util/pm_string.c

@@ -202,7 +202,7 @@ pm_string_file_init(pm_string_t *string, const char *filepath) {
     CloseHandle(file);
     *string = (pm_string_t) { .type = PM_STRING_OWNED, .source = source, .length = (size_t) file_size };
     return true;
-#else
+#elif defined(PRISM_HAS_FILESYSTEM)
     FILE *file = fopen(filepath, "rb");
     if (file == NULL) {
         return false;
@@ -241,6 +241,11 @@ pm_string_file_init(pm_string_t *string, const char *filepath) {
 
     *string = (pm_string_t) { .type = PM_STRING_OWNED, .source = source, .length = length };
     return true;
+#else
+    (void) string;
+    (void) filepath;
+    perror("pm_string_file_init is not implemented for this platform");
+    return false;
 #endif
 }