Fix sys-config/ltoize to install symlinks at proper location in Prefix. (#862)

dosym seems to silently adds $EPREFIX to some parts of its arguments,
see https://bugs.gentoo.org/615594. This is a hackish way of having
Prefix install the symlinks at the expected location.

I updated the documentation to reflect that Prefix cannot use the
make.conf.lto symlink, at it sources an absolute path that is not
present in Prefix.

Author: joeydumont

sys-config/ltoize/ltoize-0.9.11.ebuild

@@ -0,0 +1,127 @@
+# Copyright 1999-2021 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=7
+
+inherit toolchain-funcs
+
+DESCRIPTION="A configuration for portage to make building with LTO easy"
+HOMEPAGE="https://github.com/InBetweenNames/gentooLTO"
+
+#Note: there's nothing preventing this from working on stable, but the dependencies of ltoize aren't keyworded for
+#stable, so we only can do testing
+KEYWORDS="~alpha ~amd64 ~arm ~arm64 ~hppa ~ia64 ~m68k ~mips ~ppc ~ppc64 ~s390 ~sparc ~x86"
+
+SRC_URI=""
+
+LICENSE="GPL-2+"
+SLOT="0"
+IUSE="clang keep-nocommon override-flagomatic"
+
+#portage-bashrc-mv can be obtained from mv overlay
+DEPEND="
+	app-portage/portage-bashrc-mv[cflags]
+	sys-apps/portage
+	sys-devel/gcc-config
+"
+RDEPEND="${DEPEND}"
+
+#Test binutils and gcc version
+pkg_setup() {
+
+	ACTIVE_GCC=$(gcc-fullversion)
+
+	if ver_test "${ACTIVE_GCC}" -lt 10.2.0; then
+		ewarn "Warning: Active GCC version '$ACTIVE_GCC' is lower then the expected version '10.2.0', it is recommended that you use the newest GCC if you want LTO."
+		if [ "${I_KNOW_WHAT_I_AM_DOING}" != "y" ]; then
+			eerror "Aborting LTOize installation due to older GCC version '$ACTIVE_GCC' -- set I_KNOW_WHAT_I_AM_DOING=y if you want to override this behaviour."
+			die
+		else
+			ewarn "I_KNOW_WHAT_I_AM_DOING=y -- continuing anyway"
+		fi
+	fi
+
+	if [ -f "${PORTAGE_CONFIGROOT%/}/etc/portage/package.cflags" ]; then
+		eerror "${PORTAGE_CONFIGROOT%/}/etc/portage/package.cflags is a file not a directory.  Please convert package.cflags to a directory with the current contents of package.cflags being moved to a file inside it."
+		die
+	fi
+
+}
+
+pkg_preinst() {
+	ACTIVE_GCC=$(gcc-fullversion)
+	GENTOOLTO_PORTDIR=$(portageq get_repo_path ${PORTAGE_CONFIGROOT} lto-overlay)
+	LTO_PORTAGE_DIR="${GENTOOLTO_PORTDIR}/${CATEGORY}/${PN}/files"
+
+	COMMON_WORKAROUNDS=(
+		cmake-makefile.conf
+		devirtualize-at-ltrans.conf
+		graphite.conf
+		ipa-pta.conf
+		lto.conf
+		no-common-libtool.conf
+		no-plt.conf
+		no-semantic-interposition.conf
+		optimizations.conf
+		portage-bashrc-mv.conf
+		tls-dialect.conf
+		use-ld.conf
+	)
+
+	#Install make.conf settings
+	elog "Installing make.conf.lto.defines definitions for optimizations used in this overlay"
+	dosym "${LTO_PORTAGE_DIR}/make.conf.lto.defines" "${PORTAGE_CONFIGROOT#${EPREFIX}}/etc/portage/make.conf.lto.defines"
+
+	elog "Installing make.conf.lto default full optimization config for make.conf"
+	dosym "${LTO_PORTAGE_DIR}/make.conf.lto" "${PORTAGE_CONFIGROOT#${EPREFIX}}/etc/portage/make.conf.lto"
+
+	#Install main workarounds files
+	for i in "${COMMON_WORKAROUNDS[@]}"; do
+		elog "Installing package.cflags ${i} override"
+		dosym "${LTO_PORTAGE_DIR}/package.cflags/${i}" "${PORTAGE_CONFIGROOT#${EPREFIX}}/etc/portage/package.cflags/${i}"
+	done
+
+	#Install -fno-common workarounds file
+	use keep-nocommon && dosym "${LTO_PORTAGE_DIR}/package.cflags/no-common.conf" \
+	"${PORTAGE_CONFIGROOT#${EPREFIX}%/}/etc/portage/package.cflags/no-common.conf"
+
+	# Install Clang LTO workarounds
+	use clang && dosym "${LTO_PORTAGE_DIR}/package.cflags/clang.conf" \
+	"${PORTAGE_CONFIGROOT#${EPREFIX}%/}/etc/portage/package.cflags/clang.conf"
+
+	#Install patch framework
+	elog "Installing bashrc.d hook symlink to apply LTO patches directly from lto-overlay"
+	dosym "${LTO_PORTAGE_DIR}/bashrc.d/41-lto-patch.sh" "${PORTAGE_CONFIGROOT#${EPREFIX}}/etc/portage/bashrc.d/41-lto-patch.sh"
+
+	#Optional: install flag-o-matic overrides
+	if use override-flagomatic; then
+		ewarn "Installing bashrc.d hook to override strip-flags and replace-flags functions in flag-o-matic.  This is an experimental feature!"
+		dosym "${LTO_PORTAGE_DIR}/bashrc.d/42-lto-flag-o-matic.sh" "${PORTAGE_CONFIGROOT#${EPREFIX}}/etc/portage/bashrc.d/42-lto-flag-o-matic.sh"
+		dosym "${LTO_PORTAGE_DIR}/package.cflags/flag-o-matic.conf" "${PORTAGE_CONFIGROOT#${EPREFIX}}/etc/portage/package.cflags/flag-o-matic.conf"
+	fi
+
+	elog "Installing bashrc.d hook symlink to override package libtool lt_cv_sys_global_symbol_pipe and lt_cv_sys_global_symbol_to_cdecl"
+	dosym "${LTO_PORTAGE_DIR}/bashrc.d/43-lto-no-common.sh" "${PORTAGE_CONFIGROOT#${EPREFIX}}/etc/portage/bashrc.d/43-lto-no-common.sh"
+}
+
+pkg_postinst()
+{
+	elog "If you have not done so, you will need to modify your make.conf settings to enable LTO building on your system."
+	elog "A symlink has been placed in ${PORTAGE_CONFIGROOT%/}/etc/portage/make.conf.lto that can be used as a basis for these modifications."
+	elog "See README.md for more details."
+	elog "lto-overlay and ltoize are part of a project to help find undefined behaviour in C and C++ programs through the use of aggressive compiler optimizations."
+	elog "One of the aims of this project is also to improve the performance of linux distributions through these mechanisms as well."
+	elog "Occasionally, you will experience breakage due to LTO problems.  These are documented in the README.md of this repository."
+	elog "If you add an override for a particular package, please consider sending a pull request upstream so that other users of this repository can benefit."
+	ewarn "You will require a complete system rebuild in order to gain the benefits of LTO system-wide."
+	echo
+	elog "Please consider reading the README.md at the root of this repository before attempting to rebuild your system to familiarize yourself with the goals of this project and potential pitfalls you could run into."
+	echo
+	ewarn "This is an experimental project and should not be used on a stable system in its current state."
+
+	BINUTILS_VER=$(binutils-config ${CHOST} -c | sed -e "s/.*-//")
+
+	if ver_test "${BINUTILS_VER}" -lt 2.34; then
+		ewarn "Warning: active binutils version < 2.34, it is recommended that you use the newest binutils for LTO."
+	fi
+}