distutils-r1.eclass: Revert "Support backend-path in pyproject.toml"

This does not handle packages without pyproject.toml correctly.

Reverts: c8b8dc11f7
Closes: https://bugs.gentoo.org/836660
Closes: https://bugs.gentoo.org/836661
Closes: https://bugs.gentoo.org/836662
Signed-off-by: Michał Górny <mgorny@gentoo.org>

eclass/distutils-r1.eclass

@@ -1015,15 +1015,8 @@ distutils_pep517_install() {
 	einfo "  Building the wheel for ${PWD#${WORKDIR}/} via ${build_backend}"
 	local wheel=$(
 		"${EPYTHON}" - 3>&1 >&2 <<-EOF || die "Wheel build failed"
-			import os
-			import sys
-			import tomli
-
-			sys.path[:0] = (tomli.load(open("pyproject.toml", "rb"))
-					.get("build-system", {})
-					.get("backend-path", []))
-
 			import ${build_backend%:*}
+			import os
 			print(${build_backend/:/.}.build_wheel(os.environ['WHEEL_BUILD_DIR']),
 				file=os.fdopen(3, 'w'))
 		EOF