cmake: remove CMAKE_REQUIRED_* instances

The tcl ones has not been required for over a decade since commit
ffdba5b24 ("Remove check of Tcl_CreateNamespace in cmake build (not used
any more) (bug #27119)").

While the top-level one, with the EXTRA_LIBS reshuffle/consolidation a
few commits ago.

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

CMakeLists.txt

@@ -313,7 +313,6 @@ 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()

src/plugins/tcl/CMakeLists.txt

@@ -28,8 +28,6 @@ add_library(tcl MODULE
 set_target_properties(tcl PROPERTIES PREFIX "")
 
 if(TCL_FOUND)
-  set(CMAKE_REQUIRED_INCLUDES "${TCL_INCLUDE_PATH}")
-  set(CMAKE_REQUIRED_LIBRARIES "${TCL_LIBRARY}")
   include_directories(${TCL_INCLUDE_PATH})
   set(CMAKE_MODULE_LINKER_FLAGS "${CMAKE_MODULE_LINKER_FLAGS} ${TCL_LFLAGS}")
   target_link_libraries(tcl ${TCL_LIBRARY} weechat_plugins_scripts coverage_config)