[fuzz] Add fuzzing script from kcc@

https://github.com/behdad/harfbuzz/issues/139

test/fuzzing/hb-fuzzer.cc

@@ -0,0 +1,47 @@
+#include <stddef.h>
+#include "src/hb.h"
+#include "src/hb-ot.h"
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
+  const char text[] = "ABCDEXYZ123@_%&)*$!";
+
+  hb_blob_t *blob = hb_blob_create((const char *)data, size,
+                                   HB_MEMORY_MODE_READONLY, NULL, NULL);
+  hb_face_t *face = hb_face_create(blob, 0);
+  hb_font_t *font = hb_font_create(face);
+  hb_ot_font_set_funcs(font);
+  hb_font_set_scale(font, 12, 12);
+
+  hb_buffer_t *buffer = hb_buffer_create();
+  hb_buffer_add_utf8(buffer, text, -1, 0, -1);
+  hb_buffer_guess_segment_properties(buffer);
+
+  hb_shape(font, buffer, NULL, 0);
+
+  hb_buffer_destroy(buffer);
+  hb_font_destroy(font);
+  hb_face_destroy(face);
+  hb_blob_destroy(blob);
+  return 0;
+}
+
+#ifdef MAIN
+#include <iostream>
+#include <iterator>
+#include <fstream>
+#include <assert.h>
+
+std::string FileToString(const std::string &Path) {
+  std::ifstream T(Path.c_str());
+  return std::string((std::istreambuf_iterator<char>(T)),
+                     std::istreambuf_iterator<char>());
+}
+
+int main(int argc, char **argv) {
+  for (int i = 1; i < argc; i++) {
+    std::string s = FileToString(argv[i]);
+    std::cout << argv[i] << std::endl;
+    LLVMFuzzerTestOneInput((const unsigned char*)s.data(), s.size());
+  }
+}
+#endif