CMake: remove TEST_syslog but not FEATURE_syslog

This feature was already in AUTODETECT OFF. That means we only enabled
syslog() support if the user explicitly asked for it, which reasonably
means they have the API. The API is also POSIX.1-2001 and 4.2BSD, so
everyone has it.

Saves 350 ms of CMake time, because the test was compiled even though
AUTODETECT was OFF.

Change-Id: Ifbf974a4d10745b099b1fffd1777572e74a90043
Reviewed-by: Alexey Edelev <alexey.edelev@qt.io>

src/corelib/configure.cmake

@@ -414,23 +414,6 @@ renameat2(AT_FDCWD, argv[1], AT_FDCWD, argv[2], RENAME_NOREPLACE | RENAME_WHITEO
 }
 ")
 
-# syslog
-qt_config_compile_test(syslog
-    LABEL "syslog"
-    CODE
-"#include <syslog.h>
-
-int main(void)
-{
-    /* BEGIN TEST: */
-openlog(\"qt\", 0, LOG_USER);
-syslog(LOG_INFO, \"configure\");
-closelog();
-    /* END TEST: */
-    return 0;
-}
-")
-
 # cpp_winrt
 qt_config_compile_test(cpp_winrt
     LABEL "cpp/winrt"
@@ -647,7 +630,6 @@ qt_feature("slog2" PRIVATE
 qt_feature("syslog" PRIVATE
     LABEL "syslog"
     AUTODETECT OFF
-    CONDITION TEST_syslog
 )
 qt_feature("sysv_sem" PRIVATE
     LABEL "System V / XSI semaphores"