python-cython: mangle scripts to use /usr/bin/env python

This prevents runtime failure "bad interpreter: No such file or directory"
from running native cython when the native python is installed
at a long path, exceeding the 128-character limit for shebang lines
on linux. Exceeding the limit was already possible when using a long
path for topdir, but it got easier to exceed after the switch to per-recipe
sysroots.

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>

meta-python/recipes-devtools/python/python-cython.inc

@@ -17,3 +17,10 @@ RDEPENDS_${PN}_class-target += "\
     ${PYTHON_PN}-subprocess \
     ${PYTHON_PN}-shell \
 "
+
+do_install_append() {
+	# Make sure we use /usr/bin/env python
+	for PYTHSCRIPT in `grep -rIl '^#!.*python' ${D}`; do
+		sed -i -e '1s|^#!.*|#!/usr/bin/env ${PYTHON_PN}|' $PYTHSCRIPT
+	done
+}