cmd/go: add missing doc for GOOS and GOARCH

LGTM=r
R=golang-codereviews, r
CC=golang-codereviews
https://golang.org/cl/133900043

diff --git a/src/cmd/go/doc.go b/src/cmd/go/doc.go
index 19fe5cd3efa23c484b3318b3b1c368867494914c..0d4e2638919f8dea17e23dc22827ca87cd85d5a1 100644 (file)
--- a/src/cmd/go/doc.go
+++ b/src/cmd/go/doc.go
@@ -250,6 +250,10 @@ quoted string appears a single argument to the generator.
 
 Go generate sets several variables when it runs the generator:
 
+       $GOARCH
+               The execution architecture (arm, amd64, etc.)
+       $GOOS
+               The execution operating system (linux, windows, etc.)
        $GOFILE
                The base name of the file.
        $GOPACKAGE