Improve logging of BPF generation errors

[tgraf]

Produces clear and easy to understand error messages:

WARN[0002] + OPTS='-DSECLABEL=2 -DPOLICY_MAP=cilium_policy_reserved_2 -DCALLS_MAP=cilium_calls_overlay_2'
WARN[0002] + IN=bpf_overlay.c
WARN[0002] + OUT=bpf_overlay.o
WARN[0002] ++ ip link show cilium_vxlan


WARN[0002] ++ grep ether
WARN[0002] ++ awk '{print $2}'
WARN[0002] + NODE_MAC=76:f9:95:b7:8f:81
WARN[0002] ++ mac2array 76:f9:95:b7:8f:81
WARN[0002] ++ echo '{0x76,0xf9,0x95,0xb7,0x8f,0x81}'
WARN[0002] + NODE_MAC='{.addr={0x76,0xf9,0x95,0xb7,0x8f,0x81}}'
WARN[0002] + clang -D__NR_CPUS__=2 -O2 -target bpf -I/run/cilium/state/globals -I. -I/var/lib/cilium/bpf/include -DENABLE_ARP_RESPONDER -DHANDLE_NS -Wno-address-of-packed-member -Wno-unknown-warning-option -DSECLABEL=2 -DPOLICY_MAP=cilium_policy_reserved_2 -DCALLS_MAP=cilium_calls_overlay_2 '-DNODE_MAC={.addr={0x76,0xf9,0x95,0xb7,0x8f,0x81}}' -c /var/lib/cilium/bpf/bpf_overlay.c -o bpf_overlay.o
WARN[0002] In file included from /var/lib/cilium/bpf/bpf_overlay.c:27:
WARN[0002] In file included from /var/lib/cilium/bpf/lib/common.h:21:
WARN[0002] /run/cilium/state/globals/bpf_features.h:1:2: error: unterminated conditional directive
WARN[0002] #ifndef BPF_FEATURES_H_
WARN[0002]  ^
WARN[0002] 1 error generated.
ERRO[0002] Error while initializing daemon: exit status 1

FATA[0002] Error while creating daemon: exit status 1

[aanm]

This is awesome!

[ianvernon]

This is great, thanks for taking care of this.