pkg-perl: set PERL_USE_UNSAFE_INC

Recent perls are built with the `default_inc_excludes_dot` option.
As many CPAN modules rely on '.' in @INC, the toolchain
must set `PERL_USE_UNSAFE_INC`.

Signed-off-by: Francois Perrad <francois.perrad@gadz.org>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/pkg-perl.mk

@@ -20,7 +20,7 @@
 ################################################################################
 
 PERL_ARCHNAME = $(ARCH)-linux
-PERL_RUN = PERL5LIB= $(HOST_DIR)/usr/bin/perl
+PERL_RUN = PERL5LIB= PERL_USE_UNSAFE_INC=1 $(HOST_DIR)/usr/bin/perl
 
 ################################################################################
 # inner-perl-package -- defines how the configuration, compilation and