perl-module.eclass: respect prefix for Module::Build

https://metacpan.org/pod/Module::Build::Cookbook#Installing-in-the-same-location-as-ExtUtils::MakeMaker

Closes: https://bugs.gentoo.org/981502
Signed-off-by: Sam James <sam@gentoo.org>

eclass/perl-module.eclass

@@ -295,6 +295,7 @@ perl-module_src_configure() {
 		fi
 
 		set -- \
+			--prefix "${EPREFIX}"/usr \
 			--installdirs=vendor \
 			--libdoc= \
 			--create_packlist=1 \