CMakeLists.txt uses deprecated singular CURL_LIBRARY, breaking libcurl linking on modern CMake

Hello,

I ran into a build issue with SWORD 1.9.0 while packaging a SWORD-based
application for Flathub against a recent toolchain (CMake 3.28+,
freedesktop-sdk 25.08). I tracked it down to what I believe is a small
upstream bug, and wanted to report it in case you'd like to fix it for
the next release.

Symptom
-------
libsword.so builds successfully but has no NEEDED entry for libcurl
and ships with unresolved curl_easy_* symbols. Any downstream binary
that links against libsword (including SWORD's own buildtest) then
fails to link with:

undefined reference to `curl_easy_init'
undefined reference to `curl_easy_perform'
undefined reference to `curl_easy_setopt'
undefined reference to `curl_easy_cleanup'
undefined reference to `curl_global_init'
undefined reference to `curl_global_cleanup'

Despite CMake reporting curl as found:

– cURL: system and /usr/include

Note the empty space between "system" and "and" — that's where the
curl library path was supposed to print.

Root cause
----------
In CMakeLists.txt around line 219:

SET(SWORD_LINK_LIBRARIES ${SWORD_LINK_LIBRARIES} ${CURL_LIBRARY})

This uses the singular ${CURL_LIBRARY}. Modern CMake's FindCURL.cmake
(since roughly 3.4) only sets CURL_LIBRARIES (plural) — the singular
form has been deprecated and is no longer set on current CMake
versions. The substitution therefore expands to an empty string, and
libcurl never makes it onto the link line.

The same pattern is used correctly elsewhere in the file (zlib, bzip2,
xz, icu all use the singular form, but those Find modules still set
the singular variable in modern CMake).

Suggested fix
-------------
A one-line change to CMakeLists.txt:

— a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -216,7 +216,7 @@ IF(WITH_CURL)
ENDIF(CURL_CONFIG_OUTPUT STREQUAL "1")
ENDIF(CURL_CONFIG)
INCLUDE_DIRECTORIES(${CURL_INCLUDE_DIRS})

• SET(SWORD_LINK_LIBRARIES ${SWORD_LINK_LIBRARIES} ${CURL_LIBRARY})
  + SET(SWORD_LINK_LIBRARIES ${SWORD_LINK_LIBRARIES} ${CURL_LIBRARIES})
  ENDIF(WITH_CURL)

I verified this against SWORD 1.9.0 on CMake 3.28 with the GNOME 50
runtime — libsword.so now correctly carries libcurl.so.4 in its NEEDED
entries, and all downstream targets link cleanly.

Most distributions probably don't hit this because they carry their
own patches, or they use older CMake versions where the singular
variable is still set. It only becomes visible on a freshly-modern
toolchain.

Happy to send a proper merge request if a Git repo is the preferred
intake — otherwise feel free to apply the diff directly.

Thanks for SWORD — it's the backbone of a Bible study app I'm building
for the Linux desktop.

Best regards,
Andres Messina