tools: Honor Config.mk debug value, rather than setting our own

tools: Honor Config.mk debug value, rather than setting our own

Changeset 1166ecf ('tools/Rules.mk: Don't optimize debug builds; add
macro debugging information') exposed a bug whereby the autoconf stuff
in tools was setting its own debug value (defaulting to ENABLED, even
for releases) instead of honoring the value set in Config.mk.

After that changeset, if the global build has -D_FORTIFY_SOURCE
enabled (as is the default in CentOS 7 rpmbuild), then the tools build
will fail (because debug builds default to on).

There should be only one place to specify whether to build debug or
not, and Config.mk is already included by the relevant makefiles.  So
simply remove the tools/configure debug option and everything falls
into place naturally.

Signed-off-by: George Dunlap <george.dunlap@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>