only attempt to detect illumos on plausible hosts

CMakeLists.txt

@@ -61,16 +61,16 @@ if(${CMAKE_SYSTEM_NAME} STREQUAL "OpenBSD")
  endif()
 endif()
 
-if(CMAKE_SYSTEM_NAME STREQUAL "SunOS")
+if(CMAKE_HOST_SYSTEM_NAME STREQUAL "SunOS")
  # Determine if the host is running an illumos distribution:
  execute_process(COMMAND /usr/bin/uname -o OUTPUT_VARIABLE UNAME_O
  OUTPUT_STRIP_TRAILING_WHITESPACE)
 
  if (UNAME_O STREQUAL "illumos")
- set(ILLUMOS 1)
+ set(HOST_ILLUMOS 1)
  endif()
 
- if (ILLUMOS)
+ if (HOST_ILLUMOS)
  #
  # illumos systems require linking libsocket and libnsl to get various
  # networking routines sometimes found in libc on other platforms:
@@ -811,7 +811,7 @@ if(OPENSSL_NO_SSE2_FOR_TESTING)
  add_definitions(-DOPENSSL_NO_SSE2_FOR_TESTING)
 endif()
 
-if(ILLUMOS)
+if(HOST_ILLUMOS)
  #
  # CMAKE_SYSTEM_PROCESSOR unfortunately comes from the output of "uname -p",
  # which on illumos systems emits "i386". Instead, use the value from