Revert r477 "Revert r247 "Explicity invoke bash for make-standalone-toolchain.sh""

Turned out that the original issue was not fixed even in NDK r10d.

Closes Issue 269.

BUG=Issue mozc:269
TEST=compile in Ubuntu 14.04

git-svn-id: https://mozc.googlecode.com/svn/trunk@481 a6090854-d499-a067-5803-1114d4e51264