cmake: add feature checks for memrchr and getifaddrs

- `HAVE_MEMRCHR` for `memrchr`.
- `HAVE_GETIFADDRS` for `getifaddrs`.
  This was present in `lib/curl_config.h.cmake` but missed the detection
  logic.

To match existing autotools feature checks.

Closes #11954

CMake/Platforms/WindowsCache.cmake

@@ -88,6 +88,7 @@ if(NOT UNIX)
     set(HAVE_STRDUP 1)
     set(HAVE_STRICMP 1)
     set(HAVE_STRCMPI 1)
+    set(HAVE_MEMRCHR 0)
     set(HAVE_GETTIMEOFDAY 0)
     set(HAVE_CLOSESOCKET 1)
     set(HAVE_SIGSETJMP 0)
@@ -102,6 +103,7 @@ if(NOT UNIX)
     set(HAVE_LINUX_TCP_H 0)
     set(HAVE_GLIBC_STRERROR_R 0)
     set(HAVE_MACH_ABSOLUTE_TIME 0)
+    set(HAVE_GETIFADDRS 0)
 
     set(HAVE_GETHOSTBYNAME_R_3 0)
     set(HAVE_GETHOSTBYNAME_R_3_REENTRANT 0)