build: allow openjdk

Change-Id: I9c4a2e306edfefed00a99ec0eae322bd50969a65
kernel: allow skipping the module build

kernels that dont need modules or have modules disabled can define
TARGET_KERNEL_NO_MODULES:=true to skip building them

Change-Id: I51f00e23f47bf3c9663ae9a553e9cbe0d7ef62b0
kernel: use the same gcc version as the build

Change-Id: Ice5ea688a106119741bb6a04d4566612ef093494