build: Fix a comment about BPF_SRCFILES
build: Fix a comment about BPF_SRCFILES

We no longer dump the contents of BPF_SRCFILES variable to a file.

Fixes: #12326
Signed-off-by: Jarno Rajahalme <0f1ab0ac7dffd9db21aa539af2fd4bb04abc3ad4@covalent.io>

tgraf/cilium,cilium/cilium,tgraf/cilium,michi-covalent/cilium,cilium-team/cilium,michi-covalent/cilium,tgraf/cilium,cilium/cilium,michi-covalent/cilium,tklauser/cilium,cilium/cilium,tklauser/cilium,cilium/cilium,tgraf/cilium,cilium/cilium,michi-covalent/cilium,tgraf/cilium,tgraf/cilium,tklauser/cilium,michi-covalent/cilium,tklauser/cilium,tklauser/cilium,cilium-team/cilium