abuild depends on the gcc binary in order to define a default CBUILD value.
When using an alternative gcc version (e.g. envkernel.sh with gcc6), the
gcc binary is not installed by the envkernel.sh script.
This change sets the CBUILD env variable so that abuild doesn't need to
depend on the gcc package.
Provides a quick way to incrementally compile a kernel and push it to
device.
Example usage.
Compile the kernel:
$ cd /src/linux/
$ source /src/pmbootstrap/helpers/envkernel.sh
$ make tegra_postmarketos_defconfig
$ make -jX
Package kernel and flash to device:
$ pmbootstrap build --envkernel linux-samsung-p4wifi
$ pmbootstrap flasher flash_kernel
Modify kernel source then incremental compile, package, and flash:
$ make -jX
$ pmbootstrap build --envkernel linux-samsung-p4wifi
$ pmbootstrap flasher flash_kernel
