dev-lang/python-exec: Install python{2,3} conditionally

Closes: https://bugs.gentoo.org/693910
Signed-off-by: Michał Górny <mgorny@gentoo.org>
Closes: https://github.com/gentoo/gentoo/pull/12892
Signed-off-by: Michał Górny <mgorny@gentoo.org>

dev-lang/python-exec/python-exec-2.4.6-r1.ebuild

@@ -49,13 +49,29 @@ src_install() {
 	newins - python-exec.conf \
 		< <(sed -n -e '/^#/p' config/python-exec.conf.example)
 
+	local programs=( python )
+	local scripts=( python-config 2to3 idle pydoc pyvenv )
+	local i
+	for i in "${_PYTHON_ALL_IMPLS[@]}"; do
+		if use "python_targets_${i}"; then
+			# NB: duplicate entries are harmless
+			if python_is_python3 "${i}"; then
+				programs+=( python3 )
+				scripts+=( python3-config )
+			else
+				programs+=( python2 )
+				scripts+=( python2-config )
+			fi
+		fi
+	done
+
 	local f
-	for f in python{,2,3}; do
+	for f in "${programs[@]}"; do
 		# symlink the C wrapper for python to avoid shebang recursion
 		# bug #568974
 		dosym python-exec2c /usr/bin/"${f}"
 	done
-	for f in python{,2,3}-config 2to3 idle pydoc pyvenv; do
+	for f in "${scripts[@]}"; do
 		# those are python scripts (except for new python-configs)
 		# so symlink them via the python wrapper
 		dosym ../lib/python-exec/python-exec2 /usr/bin/"${f}"