Changes since 8.15.3:

• fix an off-by-one error in vips__token_get()
• heifsave: fix crash when passing an invalid bitdepth [kleisauke]
• webpsave: fix memory leak on error [dloebl]
• heifsave: ensure NCLX profile is freed in lossless mode [kleisauke]
• threadpool: fix a race condition in error handling [kleisauke]
• disable GLib cast checks and asserts for plain builds [kleisauke]
• fix jpeg in tiff for high Q [nahilsobh]
• threadset: fix a race condition during thread exit [kleisauke]
• fix compatibility with MSVC [Julianiolo]

Windows binaries here shortly https://github.com/libvips/build-win64-mxe/releases/tag/v8.15.4