cmake: fix setting of -Werror

Setting COMPILE_FLAGS (or COMPILE_OPTIONS) property directly does not
end up on the command line (even though it should because
add_compile_options does just that).

Also, set -Werror for tests as well, because no warnings now.

Not set for 'external' only because simply moving add_compile_options
above add_subdirectory(external) doesn't do it, and moving add_usbdirectory
down is too big of a change (it will pick up new flags).

-Werror set only for GCC on Linux, since warnings not yet
cleared for other compilers/systems.

0 files changed, 0 insertions, 0 deletions