meson: do not link pixman automatically into all targets

meson: do not link pixman automatically into all targets

The dependency on pixman is listed manually in all sourcesets that need it.
There is no need to bring into libqemuutil, since there is nothing in
util/ that needs pixman either.

Reported-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20240408155330.522792-2-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>