tvheadend: fix error compiling with ccache

tvheadend: fix error compiling with ccache

The tvheadend configure script fails to correctly handle spaces in any of
the options passed to it.  If ccache is used the configure script fails to
handle the space in the --cc option and errors.  Also the --cflags option
fails to handle multiple entries and only uses the first one.  This patch
simple removes setting the --cc and --cflags options as the configure
script will correctly use the CC and CFLAGS variables already passed in
TARGET_CONFIGURE_OPTS.

Signed-off-by: Martin Bark <martin@barkynet.com>
Cc: Yann E. MORIN <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>