diffutils: Build with posix_error_mapper.

Should fix https://dev.haiku-os.org/ticket/5431.

sys-apps/diffutils/diffutils-3.6.recipe

@@ -16,7 +16,7 @@ You can use the sdiff command to merge two files interactively."
 HOMEPAGE="https://www.gnu.org/software/diffutils/"
 COPYRIGHT="1992-2016 Free Software Foundation, Inc."
 LICENSE="GNU GPL v3"
-REVISION="1"
+REVISION="2"
 SOURCE_URI="http://ftpmirror.gnu.org/diffutils/diffutils-$portVersion.tar.xz"
 CHECKSUM_SHA256="d621e8bdd4b573918c8145f7ae61817d1be9deb4c8d2328a65cea8e11d783bd6"
 PATCHES="diffutils-$portVersion.patchset"
@@ -52,6 +52,10 @@ defineDebugInfoPackage diffutils \
 
 BUILD()
 {
+	export CFLAGS="-DB_USE_POSITIVE_POSIX_ERRORS"
+	export CXXFLAGS="-DB_USE_POSITIVE_POSIX_ERRORS"
+	export LDFLAGS="-lposix_error_mapper" 
+	
 	runConfigure ./configure \
 		--disable-gcc-warnings
 	make $jobArgs