Use $ANDROID_TOOLCHAIN set by envsetup.sh in adb_gdb and gdb_apk

Use $ANDROID_TOOLCHAIN set by envsetup.sh in adb_gdb and gdb_apk

After recent upgradation to third_party/android_tools/ndk, there is no
linux-x86 toolchain directory any more, but linux-x86_64 instead. This
causes failure of adb_gdb and gdb_apk which hard-coded linux-x86
in the scripts. As envsetup.sh already set correct $ANDROID_TOOLCHAIN,
now use it in the scripts instead of the hardcoded one.

BUG=none
NOTRY=true (presubmit passed)

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=199567

[Yaron, 2013-05-09 19:01:25]

I think Martin already fixed this: https://codereview.chromium.org/14858018/

[Xianzhu, 2013-05-09 19:57:02]

On 2013/05/09 19:01:25, Yaron wrote:
> I think Martin already fixed this: https://codereview.chromium.org/14858018/

Would you like this one which can automatically adapt to future toolchain
directory changes?

And this one also fixes gdb_apk.

[Xianzhu, 2013-05-10 16:32:11]

ping...

[Yaron, 2013-05-10 17:16:34]

lgtm

[commit-bot: I haz the power, 2013-05-10 17:18:21]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/wangxianzhu@chromium.org/15028013/7001

[commit-bot: I haz the power, 2013-05-10 17:22:12]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/wangxianzhu@chromium.org/15028013/7001

[commit-bot: I haz the power, 2013-05-10 23:14:38]

Change committed as 199567

[digit1, 2013-05-13 08:27:24]

Sorry, I was on vacation and didn't see this.

I'm pretty sure we want to get rid of build/android/envsetup.sh and replace this
with a script like build/gyp_chromium that doesn't modify the environment. This
change will make this even more difficult.

I think we should have instead changed the logic to detect both 64-bit and
32-bit toolchain binaries properly. I'll upload a new patch later to do that
properly then.