GCE: Add /usr/src and /usr/ports to METALOG

We ship these in order to comply with GCE Marketplace rules about
providing source code and licenses for all the software we ship as
part of images.

Reviewed by:	markj
MFC after:	immediately (15.0-RC2)
Differential Revision:	https://reviews.freebsd.org/D53796

release/tools/gce.conf

@@ -98,6 +98,10 @@ EOF
 	# the image.
 	if [ -e "${DESTDIR}/../ftp/src.txz" ]; then
 		tar fxJ ${DESTDIR}/../ftp/src.txz -C ${DESTDIR}
+		( cd ${DESTDIR} && find ./usr/src ) |
+		    while read P; do
+			metalog_add_data ${P}
+		    done
 	fi
 	if [ -e "${DESTDIR}/../ftp/ports.txz" ]; then
 		tar fxJ ${DESTDIR}/../ftp/ports.txz -C ${DESTDIR}
@@ -108,6 +112,10 @@ EOF
 			    DISABLE_VULNERABILITIES=YES \
 			    I_DONT_CARE_IF_MY_BUILDS_TARGET_THE_WRONG_RELEASE=YES
 		done
+		( cd ${DESTDIR} && find ./usr/ports ) |
+		    while read P; do
+			metalog_add_data ${P}
+		    done
 	fi
 
 	## XXX: Verify this is needed.  I do not see this requirement