cpan_build: Fix cmaker Build.PL module builds

cpan_build: Fix cmaker Build.PL module builds

Certain cpan Build.PL based modules were failing to build due to
the host's config information being used instead of the targets.

This patch sets the appropriate variables to ensure the modules
get the correct configuration from the target config_heavy.pl script.

It also ensures the linker is CCLD, not LD since the LDFLAGS contain
-Wl,XXX options and build failures result if LD is used.

libencode-detect-perl is a module which tests this class extensively.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>