all: add go:build comments for .m and .c files

Change-Id: I24fbde8ec50be43000b9fcf3e7801f1ad25238cb
Reviewed-on: https://go-review.googlesource.com/c/mobile/+/374498
Run-TryBot: Hajime Hoshi <hajimehoshi@gmail.com>
Trust: Hajime Hoshi <hajimehoshi@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>

app/android.c

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build android
 // +build android
 
 #include <android/log.h>

app/darwin_desktop.m

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build darwin && !ios
 // +build darwin
 // +build !ios
 

app/darwin_ios.m

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build darwin && ios
 // +build darwin
 // +build ios
 

app/x11.c

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build linux && !android
 // +build linux,!android
 
 #include "_cgo_export.h"

bind/objc/SeqBench.m

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build ignore
 // +build ignore
 
 #import <Foundation/Foundation.h>

bind/objc/SeqCustom.m

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build ignore
 // +build ignore
 
 #import <Foundation/Foundation.h>

bind/objc/SeqTest.m

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build ignore
 // +build ignore
 
 #import <Foundation/Foundation.h>

bind/objc/SeqWrappers.m

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build ignore
 // +build ignore
 
 @import ObjectiveC.message;

exp/sensor/android.c

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build android
 // +build android
 
 #include <stdlib.h>

exp/sensor/darwin_armx.m

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build darwin && (arm || arm64)
 // +build darwin
 // +build arm arm64
 

gl/work.c

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build darwin || linux || openbsd
 // +build darwin linux openbsd
 
 #include <stdlib.h>