cmake/Find: add iphlpapi for c-ares, omit syslibs if dep not found

- add `iphlpapi` library for c-ares.
  Ref: 082d98ba6b

- fix to not add system libs if the dependency was not found.
  librtmp, Rustls, wolfSSL
  Follow-up to 421e592db2 #15832
  Follow-up to 7bab201abe #15193

Closes #16089

CMake/FindCares.cmake

@@ -90,3 +90,7 @@ else()
 
   mark_as_advanced(CARES_INCLUDE_DIR CARES_LIBRARY)
 endif()
+
+if(CARES_FOUND AND WIN32)
+  list(APPEND CARES_LIBRARIES "iphlpapi")  # for if_indextoname and others
+endif()

CMake/FindLibrtmp.cmake

@@ -97,6 +97,6 @@ else()
   endif()
 endif()
 
-if(WIN32)
+if(LIBRTMP_FOUND AND WIN32)
   list(APPEND LIBRTMP_LIBRARIES "winmm")
 endif()

CMake/FindRustls.cmake

@@ -71,7 +71,8 @@ else()
   mark_as_advanced(RUSTLS_INCLUDE_DIR RUSTLS_LIBRARY)
 endif()
 
-if(APPLE)
+if(RUSTLS_FOUND)
+  if(APPLE)
     find_library(SECURITY_FRAMEWORK NAMES "Security")
     mark_as_advanced(SECURITY_FRAMEWORK)
     if(NOT SECURITY_FRAMEWORK)
@@ -85,7 +86,7 @@ if(APPLE)
       message(FATAL_ERROR "Foundation framework not found")
     endif()
     list(APPEND RUSTLS_LIBRARIES "-framework Foundation")
-elseif(NOT WIN32)
+  elseif(NOT WIN32)
     find_library(PTHREAD_LIBRARY NAMES "pthread")
     if(PTHREAD_LIBRARY)
       list(APPEND RUSTLS_LIBRARIES ${PTHREAD_LIBRARY})
@@ -103,4 +104,5 @@ elseif(NOT WIN32)
       list(APPEND RUSTLS_LIBRARIES ${MATH_LIBRARY})
     endif()
     mark_as_advanced(MATH_LIBRARY)
+  endif()
 endif()

CMake/FindWolfSSL.cmake

@@ -90,7 +90,7 @@ else()
   mark_as_advanced(WOLFSSL_INCLUDE_DIR WOLFSSL_LIBRARY)
 endif()
 
-if(NOT WIN32)
+if(WOLFSSL_FOUND AND NOT WIN32)
   find_library(MATH_LIBRARY NAMES "m")
   if(MATH_LIBRARY)
     list(APPEND WOLFSSL_LIBRARIES ${MATH_LIBRARY})  # for log and pow