cmake: consolidate non-linux library handling

Move the handling to the top-level, adding it _once_ to EXTRA_LIBS.
Thus avoiding some duplication across the board.

Note that final handling varies a bit, namely:
 - OpenBSD/intl should be handled via the existing cmake/FindGettext.cmake
 - Darwin/resolv should not be needed since commit e98a32373 ("core: check
   if res_init requires linking with libresolv")
 - the backtrace/execinfo handling has been consolidated and moved

In the unlikely case of unwanted over-linking, the platforms can add
`-Wl,--as-needed` to their linker flags. Something which is strongly
encouraged and has been the default across multiple (linux) distros for
years.

Alternatively, if move quirks are needed they should be handled in a
single place.

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>

CMakeLists.txt

@@ -311,6 +311,25 @@ else()
   add_custom_target(translations COMMAND true)
 endif()
 
+if(${CMAKE_SYSTEM_NAME} STREQUAL "FreeBSD")
+  find_library(EXECINFO_LIB_PATH execinfo /usr/local/lib)
+  set(CMAKE_REQUIRED_LIBRARIES "${EXECINFO_LIB_PATH}")
+  check_function_exists(backtrace HAVE_BACKTRACE)
+  list(APPEND EXTRA_LIBS "execinfo")
+else()
+  check_symbol_exists(backtrace "execinfo.h" HAVE_BACKTRACE)
+endif()
+
+if(${CMAKE_SYSTEM_NAME} STREQUAL "Haiku")
+  list(APPEND EXTRA_LIBS "network")
+else()
+  list(APPEND EXTRA_LIBS "pthread")
+endif()
+
+if(${CMAKE_SYSTEM_NAME} STREQUAL "SunOS")
+  list(APPEND EXTRA_LIBS "socket" "nsl")
+endif()
+
 list(APPEND EXTRA_LIBS "m")
 
 add_subdirectory(src)

src/core/CMakeLists.txt

@@ -81,14 +81,6 @@ set(LIB_CORE_SRC
 include(CheckSymbolExists)
 check_symbol_exists(flock "sys/file.h" HAVE_FLOCK)
 
-if(${CMAKE_SYSTEM_NAME} STREQUAL "FreeBSD")
-  find_library(EXECINFO_LIB_PATH execinfo /usr/local/lib)
-  set(CMAKE_REQUIRED_LIBRARIES "${EXECINFO_LIB_PATH}")
-  check_function_exists(backtrace HAVE_BACKTRACE)
-else()
-  check_symbol_exists(backtrace "execinfo.h" HAVE_BACKTRACE)
-endif()
-
 if(ENABLE_ZSTD)
   include_directories(${LIBZSTD_INCLUDE_DIRS})
 endif()

src/gui/curses/CMakeLists.txt

@@ -21,22 +21,6 @@
 # along with WeeChat.  If not, see <https://www.gnu.org/licenses/>.
 #
 
-if(${CMAKE_SYSTEM_NAME} STREQUAL "FreeBSD" AND HAVE_BACKTRACE)
-  list(APPEND EXTRA_LIBS "execinfo")
-endif()
-
-if(${CMAKE_SYSTEM_NAME} STREQUAL "SunOS")
-  list(APPEND EXTRA_LIBS "socket" "nsl")
-endif()
-
-if(${CMAKE_SYSTEM_NAME} STREQUAL "Haiku")
-  list(APPEND EXTRA_LIBS "network")
-endif()
-
-if(NOT ${CMAKE_SYSTEM_NAME} STREQUAL "Haiku")
-  list(APPEND EXTRA_LIBS "pthread")
-endif()
-
 if(ENABLE_NCURSES)
   subdirs(normal)
 endif()

tests/fuzz/CMakeLists.txt

@@ -40,27 +40,6 @@ if(NOT CYGWIN)
   add_definitions(-fPIC)
 endif()
 
-if(${CMAKE_SYSTEM_NAME} STREQUAL "FreeBSD" AND HAVE_BACKTRACE)
-  list(APPEND EXTRA_LIBS "execinfo")
-endif()
-
-if(${CMAKE_SYSTEM_NAME} STREQUAL "SunOS")
-  list(APPEND EXTRA_LIBS "socket" "nsl")
-endif()
-
-if(${CMAKE_SYSTEM_NAME} STREQUAL "Haiku")
-  list(APPEND EXTRA_LIBS "network")
-endif()
-
-if(NOT ${CMAKE_SYSTEM_NAME} STREQUAL "Haiku")
-  list(APPEND EXTRA_LIBS "pthread")
-endif()
-
-if(${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
-  # link with resolv lib on macOS
-  list(APPEND EXTRA_LIBS "resolv")
-endif()
-
 list(APPEND FUZZ_TARGET_LINK
   weechat_core
   weechat_plugins

tests/unit/CMakeLists.txt

@@ -206,17 +206,6 @@ endif()
 
 add_library(weechat_unit_tests_plugins MODULE ${LIB_WEECHAT_UNIT_TESTS_PLUGINS_SRC})
 
-if(${CMAKE_SYSTEM_NAME} STREQUAL "FreeBSD" OR ${CMAKE_SYSTEM_NAME} STREQUAL "OpenBSD")
-  list(APPEND EXTRA_LIBS "intl")
-  if(HAVE_BACKTRACE)
-    list(APPEND EXTRA_LIBS "execinfo")
-  endif()
-endif()
-
-if(NOT ${CMAKE_SYSTEM_NAME} STREQUAL "Haiku")
-  list(APPEND EXTRA_LIBS "pthread")
-endif()
-
 # binary to run tests
 set(WEECHAT_TESTS_SRC
   tests.cpp tests.h