package/gutenprint: replaces -static with -static-libtool-libs

package/gutenprint: replaces -static with -static-libtool-libs

gutenprint rely on the original behaviour of -static, but since commit
in buildroot "support/libtool: make -static behave like -all-static" [1],
the build of genppd is broken.

genppd need to be build statically otherwise the following warning appears:
***WARNING: Use of --disable-static-genppd or --disable-static
            when building CUPS is very dangerous.  The build may
            fail when building the PPD files, or may *SILENTLY*
            build incorrect PPD files or cause other problems.
            Please review the README and release notes carefully!

[1] http://git.buildroot.net/buildroot/commit/?id=97703978ac870ce2b14ad144f8e082de82aa2c64

Fixes:
http://autobuild.buildroot.net/results/55f/55f78104d7a5d11baf5650ac12aaa1b23c2b7743/build-end.log
http://autobuild.buildroot.net/results/fc8/fc8cfe3f27ceaca70c7471c44305317c66cb0eea/build-end.log

Signed-off-by: Romain Naour <romain.naour@openwide.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>