cmake: use the BSD variable

- use `BSD` in addition to backwards-compatible method.
- add `BSD` to the configuration log and `buildinfo.txt` if detected.
- add `BSD` tag to `buildinfo.txt` also via `./configure`.

The `BSD` variable is supported by CMake 3.25.0 and upper.

Ref: https://cmake.org/cmake/help/latest/variable/BSD.html

Closes #15367

CMake/OtherTests.cmake

@@ -90,7 +90,7 @@ elseif(APPLE OR
        CMAKE_SYSTEM_NAME STREQUAL "NetBSD" OR
        CMAKE_SYSTEM_NAME STREQUAL "SunOS")
   set(HAVE_GETADDRINFO_THREADSAFE TRUE)
-elseif(CMAKE_SYSTEM_NAME MATCHES "BSD")
+elseif(BSD OR CMAKE_SYSTEM_NAME MATCHES "BSD")
   set(HAVE_GETADDRINFO_THREADSAFE FALSE)
 endif()
 

CMakeLists.txt

@@ -99,6 +99,9 @@ endif()
 if(UNIX)
   set(_target_flags "${_target_flags} UNIX")
 endif()
+if(BSD)
+  set(_target_flags "${_target_flags} BSD")
+endif()
 if(WIN32)
   set(_target_flags "${_target_flags} WIN32")
 endif()

acinclude.m4

@@ -1552,6 +1552,10 @@ AC_DEFUN([CURL_PREPARE_BUILDINFO], [
       *-*-*bsd*|*-*-aix*|*-*-hpux*|*-*-interix*|*-*-irix*|*-*-linux*|*-*-solaris*|*-*-sunos*|*-apple-*|*-*-cygwin*|*-*-msys*)
         curl_pflags="${curl_pflags} UNIX";;
     esac
+    case $host in
+      *-*-*bsd*)
+        curl_pflags="${curl_pflags} BSD";;
+    esac
   fi
   if test "$curl_cv_cygwin" = 'yes'; then
     curl_pflags="${curl_pflags} CYGWIN"