[LU-18678] dkms in-kernel on SUSE default kernel source dir fix

• Type: Bug
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.17.0
• Severity: 3
• Assignee: Shaun Tancheff
• Reporter: Shaun Tancheff

Description

From dkms the default $kernel_source_dir will be
@MODDIR@/$kernelver/build
unless otherwise specified with the --kernelsourcedir option.

Unfortunately the check for kernel headers will fail as only
the generated headers are available from the 'build' symbolic
link on SUSE.

Probe for the 'source' symbolic link if it points to a directory
with 'include/linux' proceed to prefer it when checking for
in-kernel rdma support.