configure no longer errors when libpsl is not found and not explicitly disabled

[ryandesign]

I did this

./configure --without-ssl

I expected the following

configure: error: libpsl was not found

curl/libcurl version

8.9.1

operating system

macOS 12

[ryandesign]

Your bug reporting template is cumbersome because it has no place to add additional comments.

A big deal was made about how curl 8.6.0 would now fail to configure if libpsl was not found and not explicitly disabled:

% ./configure --without-ssl
...
checking for library containing psl_builtin... no
configure: error: libpsl was not found

That feature appears to have gone away in curl 8.7.0 when the libpsl detection was rewritten to use pkg-config in 9b3f67e. It no longer fails when libpsl is not found even when libpsl is not explicitly disabled:

% ./configure --without-ssl
...
checking for psl_builtin in -lpsl... no
...
configure: Configured to build curl/libcurl:
...
  PSL:              no      (--with-libpsl)