cmd/gomobile: document the GOMOBILEFLAGS, GOARCH, GOBIND plugin settings

Change-Id: I681ac02869e137f67880416743352951960f7d8a
Reviewed-on: https://go-review.googlesource.com/33950
Reviewed-by: David Crawshaw <crawshaw@golang.org>
diff --git a/cmd/gomobile/doc.go b/cmd/gomobile/doc.go
index 000a95f..fb17b6a 100644
--- a/cmd/gomobile/doc.go
+++ b/cmd/gomobile/doc.go
@@ -181,6 +181,15 @@
 
 		// Optionally, set the absolute path to the gomobile binary.
 		// GOMOBILE = "/path/to/gomobile"
+
+		// Pass extra parameters to command line. Optional.
+		// GOMOBILEFLAGS="-javapkg my.java.package"
+
+		// Absolute path to the gobind binary. Optional.
+		// GOBIND="/path/to/gobind"
+
+		// Optional list of architectures. Defaults to all supported architectures.
+		// GOARCH="arm amd64"
 	}
 
 The direct integration mode is suitable for Go packages that import Java API, Android API,
diff --git a/misc/androidstudio/README.md b/misc/androidstudio/README.md
index a70d42c..5b6c530 100644
--- a/misc/androidstudio/README.md
+++ b/misc/androidstudio/README.md
@@ -21,7 +21,7 @@
   // Absolute path to the gomobile binary. Optional.
   GOMOBILE="/mypath/bin/gomobile"
 
-  // Absolute path to the gomobile binary. Optional.
+  // Absolute path to the gobind binary. Optional.
   GOBIND="/mypath/bin/gobind"
 
   // Absolute path to the go binary. Optional.