Fix gitea's native fuzzers (google#9378)

gitea's fuzz targets now use Go native fuzzing, and they were moved into
a dedicated `fuzz` package
(go-gitea/gitea#22376).

projects/gitea/build.sh

@@ -15,10 +15,6 @@
 #
 ################################################################################
 
-# external_renderer.go belongs to the main package and is located in the same directory
-# as the fuzz tests which belong to the fuzz package. This causes a build failure and
-# no fuzzers can be built.
-rm -f $SRC/gitea/tools/external_renderer.go
-
-compile_go_fuzzer code.gitea.io/gitea/tools FuzzMarkdownRenderRaw fuzz_markdown_render_raw gofuzz
-compile_go_fuzzer code.gitea.io/gitea/tools FuzzMarkupPostProcess fuzz_markup_post_process gofuzz
+go get github.com/AdamKorcz/go-118-fuzz-build/testing
+compile_native_go_fuzzer code.gitea.io/gitea/tests/fuzz FuzzMarkdownRenderRaw fuzz_markdown_render_raw gofuzz
+compile_native_go_fuzzer code.gitea.io/gitea/tests/fuzz FuzzMarkupPostProcess fuzz_markup_post_process gofuzz