Only clean the relevant installed files, not everything. This

should let a 6g build and an 8g build be done in sequence
without stepping on each other.

R=rsc
DELTA=2  (0 added, 0 deleted, 2 changed)
OCL=35478
CL=35481

src/clean.bash

@@ -3,8 +3,8 @@
 # Use of this source code is governed by a BSD-style
 # license that can be found in the LICENSE file.
 
-rm -rf $GOROOT/pkg/[0-9a-zA-Z_]*
-rm -f $GOROOT/lib/*.[6a]
+rm -rf $GOROOT/pkg/${GOOS}_$GOARCH
+rm -f $GOROOT/lib/*.a
 for i in lib9 libbio libcgo libmach libregexp cmd pkg \
 	../misc/cgo/gmp ../misc/cgo/stdio \
 	../usr/r/rpc ../usr/dsymonds/iterable \