dev-libs/npth: Sync with Gentoo

It's from Gentoo commit 77f67752cd0fa1d306b5d82723954ac8dbc6cd6c.

Author: krnowak

sdk_container/src/third_party/portage-stable/dev-libs/npth/npth-1.6-r1.ebuild

@@ -1,25 +1,36 @@
-# Copyright 1999-2021 Gentoo Authors
+# Copyright 1999-2023 Gentoo Authors
 # Distributed under the terms of the GNU General Public License v2
 
 EAPI=7
 
-inherit autotools
+inherit autotools flag-o-matic toolchain-funcs
 
 DESCRIPTION="New GNU Portable Threads Library"
 HOMEPAGE="https://git.gnupg.org/cgi-bin/gitweb.cgi?p=npth.git"
 SRC_URI="mirror://gnupg/${PN}/${P}.tar.bz2"
 
 LICENSE="LGPL-2.1+"
 SLOT="0"
-KEYWORDS="~alpha amd64 arm arm64 hppa ~ia64 ~m68k ~mips ppc ppc64 ~riscv ~s390 sparc x86 ~x64-cygwin ~amd64-linux ~x86-linux ~ppc-macos ~x64-macos ~sparc-solaris ~sparc64-solaris ~x64-solaris ~x86-solaris"
+KEYWORDS="~alpha amd64 arm arm64 hppa ~ia64 ~loong ~m68k ~mips ppc ppc64 ~riscv ~s390 sparc x86 ~amd64-linux ~x86-linux ~arm64-macos ~ppc-macos ~x64-macos ~x64-solaris"
+IUSE="test"
+RESTRICT="!test? ( test )"
 
 src_prepare() {
 	default
 	eautoreconf
 }
 
 src_configure() {
-	econf --disable-static
+	# ideally we want !tc-ld-is-bfd for best future-proofing, but it needs
+	# https://github.com/gentoo/gentoo/pull/28355
+	# mold needs this too but right now tc-ld-is-mold is also not available
+	if tc-ld-is-lld; then
+		append-ldflags -Wl,--undefined-version
+	fi
+
+	econf \
+		--disable-static \
+		$(use_enable test tests)
 }
 
 src_install() {