python-utils-r1: Fix cross compilation related to use of EPREFIX.

python-utils-r1.eclass was using EPREFIX to strip the leading part of
the sysroot for use with the portage ...into functions. Since EPREFIX is
empty this results paths of the form /build/${BOARD}/build/${BOARD}.
These cases were replaced with SYSROOT to yield the correct path.

BUG=chromium:921231
TEST=emerge-${BOARD} namespace-google &&
  ls /build/${BOARD}/usr/lib64/python2.7/site-packages/google/__init__.py*

Change-Id: I592dbe7f8cc419dc7bfd747afe7ceb33e59d12b2
Reviewed-on: https://chromium-review.googlesource.com/1440268
Commit-Ready: Allen Webb <allenwebb@google.com>
Tested-by: Allen Webb <allenwebb@google.com>
Reviewed-by: Chris McDonald <cjmcdonald@chromium.org>
diff --git a/eclass/python-utils-r1.eclass b/eclass/python-utils-r1.eclass
index e3cf82b..368b268 100644
--- a/eclass/python-utils-r1.eclass
+++ b/eclass/python-utils-r1.eclass
@@ -918,7 +918,7 @@
 		local PYTHON_SITEDIR=${PYTHON_SITEDIR}
 		[[ ${PYTHON_SITEDIR} ]] || python_export PYTHON_SITEDIR
 
-		d=${PYTHON_SITEDIR#${EPREFIX}}/${python_moduleroot//.//}
+		d=${PYTHON_SITEDIR#${SYSROOT}}/${python_moduleroot//.//}
 	fi
 
 	(
@@ -954,7 +954,7 @@
 	local d PYTHON_INCLUDEDIR=${PYTHON_INCLUDEDIR}
 	[[ ${PYTHON_INCLUDEDIR} ]] || python_export PYTHON_INCLUDEDIR
 
-	d=${PYTHON_INCLUDEDIR#${EPREFIX}}
+	d=${PYTHON_INCLUDEDIR#${SYSROOT}}
 
 	(
 		insopts -m 0644