dev-python/pycparser: trick tests into using CPP variable

Closes: https://bugs.gentoo.org/719934
Signed-off-by: Mike Gilbert <floppym@gentoo.org>

dev-python/pycparser/pycparser-2.20.ebuild

@@ -5,7 +5,7 @@ EAPI=7
 
 PYTHON_COMPAT=( python2_7 python3_{6,7,8} pypy3 )
 
-inherit distutils-r1
+inherit distutils-r1 toolchain-funcs
 
 DESCRIPTION="C parser and AST generator written in Python"
 HOMEPAGE="https://github.com/eliben/pycparser"
@@ -41,9 +41,20 @@ python_compile() {
 }
 
 python_test() {
+	# Trick the tests into using CPP variable
+	# https://bugs.gentoo.org/719934
+	local CPP="$(tc-getCPP)"
+	mkdir -p "${T}"/bin || die
+	cat > "${T}"/bin/cpp <<-EOF || die
+	#!/bin/sh
+	exec ${CPP} "\$@"
+	EOF
+	chmod +x "${T}"/bin/cpp || die
+	local -x PATH="${T}/bin:${PATH}"
+
 	# change workdir to avoid '.' import
 	cd tests || die
-	"${EPYTHON}" -m unittest discover -v || die "Tests fail with ${EPYTHON}"
+	${EPYTHON} -m unittest discover -v || die "Tests fail with ${EPYTHON}"
 }
 
 python_install() {