python-utils-r1: Apply cross compilation fixes.

BUG=chromium:1111336
TEST=CQ-passes

Change-Id: Ice0f2b7a0ecfcee47b52fc069d76275ac081b981
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/eclass-overlay/+/2328994
Reviewed-by: Alex Klein <saklein@chromium.org>
Tested-by: Allen Webb <allenwebb@google.com>
Commit-Queue: Allen Webb <allenwebb@google.com>
diff --git a/eclass/python-utils-r1.eclass b/eclass/python-utils-r1.eclass
index 9bad72a..5c8152f 100644
--- a/eclass/python-utils-r1.eclass
+++ b/eclass/python-utils-r1.eclass
@@ -804,7 +804,7 @@
 	else
 		# relative to site-packages
 		local sitedir=$(python_get_sitedir)
-		d=${sitedir#${EPREFIX}}/${python_moduleroot//.//}
+		d=${sitedir#${SYSROOT}}/${python_moduleroot//.//}
 	fi
 
 	(
@@ -835,7 +835,7 @@
 	[[ ${EPYTHON} ]] || die 'No Python implementation set (EPYTHON is null).'
 
 	local includedir=$(python_get_includedir)
-	local d=${includedir#${EPREFIX}}
+	local d=${includedir#${SYSROOT}}
 
 	(
 		insopts -m 0644