Misleading cmake output about missing optional packages

Even though system versions of harfbuzz, zstd, brotli and pcre2 are correctly detected by cmake and used in the build (as shown by the compiled libraries being linked to them), cmake output shows

-- The following OPTIONAL packages have not been found:
* zstd 
* PCRE2 (required version >= 10.20) 
* unofficial-brotli 
* harfbuzz (required version >= 2.6.0)

This is quite confusing and makes it hard to distinguish which system libraries are really missing.