src/make.*: make --no-clean flag a no-op that prints a warning

This flag is undocumented and is no longer useful. Users who want to
install additional toolchains without cleaning the installed packages
should just use `go install`.

This CL changes cmd/dist to print a warning that --no-clean is
deprecated and to advise users to use `go install std cmd` instead,
and then otherwise ignores it:

```
$ ./make.bash --no-clean
Building Go cmd/dist using $GOROOT_BOOTSTRAP. (devel +b7a85e0003 linux/amd64)
warning: --no-clean is deprecated and has no effect; use 'go install std cmd' instead
Building Go toolchain1 using $GOROOT_BOOTSTRAP.
```

Fixes #47204.

Change-Id: I275031832098401a49e491e324e8de3427973630
Reviewed-on: https://go-review.googlesource.com/c/go/+/341392
Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/dist/build.go

@@ -1263,14 +1263,19 @@ func cmdbootstrap() {
 	timelog("start", "dist bootstrap")
 	defer timelog("end", "dist bootstrap")
 
-	var noBanner bool
+	var noBanner, noClean bool
 	var debug bool
 	flag.BoolVar(&rebuildall, "a", rebuildall, "rebuild all")
 	flag.BoolVar(&debug, "d", debug, "enable debugging of bootstrap process")
 	flag.BoolVar(&noBanner, "no-banner", noBanner, "do not print banner")
+	flag.BoolVar(&noClean, "no-clean", noClean, "print deprecation warning")
 
 	xflagparse(0)
 
+	if noClean {
+		xprintf("warning: --no-clean is deprecated and has no effect; use 'go install std cmd' instead\n")
+	}
+
 	// Set GOPATH to an internal directory. We shouldn't actually
 	// need to store files here, since the toolchain won't
 	// depend on modules outside of vendor directories, but if

src/make.bash

@@ -203,16 +203,10 @@ if [ "$1" = "--dist-tool" ]; then
 	exit 0
 fi
 
-buildall="-a"
-if [ "$1" = "--no-clean" ]; then
-	buildall=""
-	shift
-fi
-
 # Run dist bootstrap to complete make.bash.
 # Bootstrap installs a proper cmd/dist, built with the new toolchain.
 # Throw ours, built with Go 1.4, away after bootstrap.
-./cmd/dist/dist bootstrap $buildall $vflag $GO_DISTFLAGS "$@"
+./cmd/dist/dist bootstrap -a $vflag $GO_DISTFLAGS "$@"
 rm -f ./cmd/dist/dist
 
 # DO NOT ADD ANY NEW CODE HERE.

src/make.bat

@@ -112,20 +112,20 @@ if x%2==x--dist-tool goto copydist
 if x%3==x--dist-tool goto copydist
 if x%4==x--dist-tool goto copydist
 
-set buildall=-a
-if x%1==x--no-clean set buildall=
-if x%2==x--no-clean set buildall=
-if x%3==x--no-clean set buildall=
-if x%4==x--no-clean set buildall=
-if x%1==x--no-banner set buildall=%buildall% --no-banner
-if x%2==x--no-banner set buildall=%buildall% --no-banner
-if x%3==x--no-banner set buildall=%buildall% --no-banner
-if x%4==x--no-banner set buildall=%buildall% --no-banner
+set bootstrapflags=
+if x%1==x--no-clean set bootstrapflags=--no-clean
+if x%2==x--no-clean set bootstrapflags=--no-clean
+if x%3==x--no-clean set bootstrapflags=--no-clean
+if x%4==x--no-clean set bootstrapflags=--no-clean
+if x%1==x--no-banner set bootstrapflags=%bootstrapflags% --no-banner
+if x%2==x--no-banner set bootstrapflags=%bootstrapflags% --no-banner
+if x%3==x--no-banner set bootstrapflags=%bootstrapflags% --no-banner
+if x%4==x--no-banner set bootstrapflags=%bootstrapflags% --no-banner
 
 :: Run dist bootstrap to complete make.bash.
 :: Bootstrap installs a proper cmd/dist, built with the new toolchain.
 :: Throw ours, built with Go 1.4, away after bootstrap.
-.\cmd\dist\dist.exe bootstrap %vflag% %buildall%
+.\cmd\dist\dist.exe bootstrap -a %vflag% %bootstrapflags%
 if errorlevel 1 goto fail
 del .\cmd\dist\dist.exe
 goto end

src/make.rc

@@ -92,15 +92,10 @@ if(~ $1 --dist-tool){
 	exit
 }
 
-buildall = -a
-if(~ $1 --no-clean) {
-	buildall = ()
-	shift
-}
 # Run dist bootstrap to complete make.bash.
 # Bootstrap installs a proper cmd/dist, built with the new toolchain.
 # Throw ours, built with Go 1.4, away after bootstrap.
-./cmd/dist/dist bootstrap $vflag $buildall $*
+./cmd/dist/dist bootstrap -a $vflag $*
 rm -f ./cmd/dist/dist
 
 # DO NOT ADD ANY NEW CODE HERE.