[Cmake] Caching CHECK_INCLUDE and other results

[Amitha Perera]

Hi all

Right now, a command like
  CHECK_INCLUDE_FILE( math.h MY_TEST_RESULT )
is cached into MY_TEST_RESULT, which means
  CHECK_INCLUDE_FILE( math.h MY_TEST_RESULT )
  CHECK_INCLUDE_FILE( math.h MY_DIFFERENT_RESULT )
will run the check include test twice.

My understanding is that the two tests should always return the same
results. Thus, perhaps the results could be cached into a common
variable name depending on the include file being tested? Then the two
test would not need to be run twice.

Thoughts?

Amitha.