verbose.mk: print ERROR messages in non-verbose

Using `make -j9` only prints a subset of messages to follow the build
process progressing. However this silently skips over errors which might
be of interested. Using `make V=s` easily floods the terminal making it
hard to find error messages between the lines.

A compromise is the usage of `$(call ERROR_MESSAGE,...)` which prints a
message in red. This function is silenced in the non-verbose mode, even
if only used at a single place in `package/Makefile` where it notifies
about a OPKG corner case.

This commit moves the `ERROR_MESSAGE` definition outside of the
`OPENWRT_VERBOSE` condition and print error messages in every mode.

With this in place further error messages are possible.

Signed-off-by: Paul Spooren <mail@aparcar.org>