build: make nacl pass

Add nacl.bash, the NaCl version of all.bash.
It's a separate script because it builds a variant of package syscall
with a large zip file embedded in it, containing all the input files
needed for tests.

Disable various tests new since the last round, mostly the ones using os/exec.

Fixes #7945.

LGTM=dave
R=golang-codereviews, remyoudompheng, dave, bradfitz
CC=golang-codereviews
https://golang.org/cl/100590044
diff --git a/src/make.bash b/src/make.bash
index 0b130b6..d7b63ff 100755
--- a/src/make.bash
+++ b/src/make.bash
@@ -153,6 +153,7 @@
 buildall="-a"
 if [ "$1" = "--no-clean" ]; then
 	buildall=""
+	shift
 fi
 ./cmd/dist/dist bootstrap $buildall $GO_DISTFLAGS -v # builds go_bootstrap
 # Delay move of dist tool to now, because bootstrap may clear tool directory.