Revert "Revert "Update envsetup.sh""

This reverts commit 52f64b2efb1f3f53224fa9b9e70f089f1f3f1bf2.
Revert "Revert "Use GCC 4.9 for kernels (just a test)""

This reverts commit e1c01b525d27b0ef2e5e8f0715a44c2658f3eb5f.