[release-branch.go1.12] cmd/vendor: remove _test.go and testdata files

Binary files included in testdata directories can cause Apple’s
notarization service to reject us since they don’t abide by their
strict requirements.

To emulate go mod vendor, remove all _test.go and testdata files
from the vendor directory and update the instructions.

Updates #34986
Fixes #35747

Change-Id: I5cde905fc78838d2e3b1519dab4aeee13d8d5356
Reviewed-on: https://go-review.googlesource.com/c/go/+/208227
Run-TryBot: Andrew Bonventre <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>
Reviewed-by: Alexander Rakoczy <[email protected]>

Author: andybons

misc/nacl/testzip.proto

@@ -48,43 +48,33 @@ go	src=..
 						pprof
 							internal
 								binutils
-									testdata
-										+
+									+
 								driver
-									testdata
-										+
+									+
 								graph
-									testdata
-										+
+									+
 								report
-									testdata
-										+
-							profile
-								testdata
 									+
+							profile
+								+
 					ianlancetaylor
 						demangle
-							testdata
-								+
+							+
 				golang.org
 					x
 						arch
 							arm
 								armasm
-									testdata
-										+
+									+
 							arm64
 								arm64asm
-									testdata
-										+
+									+
 							x86
 								x86asm
-									testdata
-										+
+									+
 							ppc64
 								ppc64asm
-									testdata
-										+
+									+
 		archive
 			tar
 				testdata

src/cmd/vendor/README

@@ -22,4 +22,10 @@ commit by accident.
 
 The vendored copy of golang.org/x/tools is maintained by
 running the update-xtools.sh script in this directory,
-not by govendor.
+not by govendor.
+
+Please ensure that you remove all *_test.go and testdata
+files after updating (golang.org/issue/34986).
+
+  $ cd $GOROOT/src/cmd
+  $ find vendor | grep -E '_test.go|testdata' | xargs rm -rf