[dev.boringcrypto] make.bash: disable GOEXPERIMENT when using bootstrap toolchain

When using Go 1.4 this doesn't matter, but when using Go 1.17,
the bootstrap toolchain will complain about unknown GOEXPERIMENT settings.
Clearly GOEXPERIMENT is for the toolchain being built, not the bootstrap.

For #51940.

Change-Id: Iff77204391a5a66f7eecab1c7036ebe77e1a4e82
Reviewed-on: https://go-review.googlesource.com/c/go/+/395879
Trust: Russ Cox <[email protected]>
Run-TryBot: Russ Cox <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>

Author: rsc

src/make.bash

@@ -185,7 +185,7 @@ fi
 # Get the exact bootstrap toolchain version to help with debugging.
 # We clear GOOS and GOARCH to avoid an ominous but harmless warning if
 # the bootstrap doesn't support them.
-GOROOT_BOOTSTRAP_VERSION=$(GOOS= GOARCH= $GOROOT_BOOTSTRAP/bin/go version | sed 's/go version //')
+GOROOT_BOOTSTRAP_VERSION=$(GOOS= GOARCH= GOEXPERIMENT= $GOROOT_BOOTSTRAP/bin/go version | sed 's/go version //')
 echo "Building Go cmd/dist using $GOROOT_BOOTSTRAP. ($GOROOT_BOOTSTRAP_VERSION)"
 if $verbose; then
 	echo cmd/dist
@@ -196,7 +196,7 @@ if [ "$GOROOT_BOOTSTRAP" = "$GOROOT" ]; then
 	exit 1
 fi
 rm -f cmd/dist/dist
-GOROOT="$GOROOT_BOOTSTRAP" GOOS="" GOARCH="" GO111MODULE=off "$GOROOT_BOOTSTRAP/bin/go" build -o cmd/dist/dist ./cmd/dist
+GOROOT="$GOROOT_BOOTSTRAP" GOOS="" GOARCH="" GO111MODULE=off GOEXPERIMENT= "$GOROOT_BOOTSTRAP/bin/go" build -o cmd/dist/dist ./cmd/dist
 
 # -e doesn't propagate out of eval, so check success by hand.
 eval $(./cmd/dist/dist env -p || echo FAIL=true)