Revert "build: Document outputexports"

This reverts commit d4d9ac2d.

This is broken:
core:static_lib(master): sanitycheck -T .
Generating LALR tables
Cleaning output directory /home/nashif/Work/zephyr/sanity-out
Selecting default platforms per test case
Building testcase defconfigs...
1 tests selected, 28 tests discarded due to filters
total complete:   1/  1  failed:   0
1 of 1 tests passed with 0 warnings in 0 seconds
Traceback (most recent call last):
  File "//home/nashif/Work/zephyr/scripts/sanitycheck", line 1887, in <module>
    main()
  File "//home/nashif/Work/zephyr/scripts/sanitycheck", line 1879, in main
    ts.testcase_report(LAST_SANITY)
  File "//home/nashif/Work/zephyr/scripts/sanitycheck", line 1551, in testcase_report
    rowdict["ram_size"] = goal.metrics["ram_size"]
KeyError: 'ram_size'
core:static_lib(master): find -name *elf
core:static_lib(master): make pristine
make -C mylib clean
make[1]: Entering directory '/home/nashif/Work/zephyr/samples/static_lib/mylib'
Makefile:19: *** $(O) is not set.  Try `make all-mylib` from hello_world.  Stop.
make[1]: Leaving directory '/home/nashif/Work/zephyr/samples/static_lib/mylib'
Makefile:37: recipe for target 'pristine' failed
make: *** [pristine] Error 2

Change-Id: I61700b0df34790aef94a6700c7c7e0605343787f
Signed-off-by: axy <anas.nashif@intel.com>