build/pkgs/sagelib/src: Apply PEP 517 changes

Author: Matthias Koeppe

build/pkgs/sagelib/src/pyproject.toml

@@ -0,0 +1 @@
+../../../../src/pyproject.toml

build/pkgs/sagelib/src/setup.py

@@ -18,6 +18,9 @@
 ### Set source directory
 #########################################################
 
+# PEP 517 builds do not have . in sys.path
+sys.path.insert(0, os.path.dirname(__file__))
+
 import sage.env
 sage.env.SAGE_SRC = os.getcwd()
 from sage.env import *