main: pass -target to bpf2go

Use the -target flag to tell bpf2go which arch we are targeting. This
cuts down on compiling useless targets (big endian x86 anyone?)
bpf2go will automatically pass the appropriate __TARGET_ARCH_xxx.

Also use $GOARCH from as set by go generate to reduce the necessary
boilerplate.

build.go

@@ -0,0 +1,11 @@
+// SPDX-License-Identifier: GPL-2.0-only
+// Copyright (C) 2021 Authors of Cilium */
+
+//go:generate sh -c "echo Generating for $GOARCH"
+//go:generate go run github.com/cilium/ebpf/cmd/bpf2go -target $GOARCH -cc clang KProbePWRU ./bpf/kprobe_pwru.c -- -DOUTPUT_SKB -I./bpf/headers -Wno-address-of-packed-member
+//go:generate go run github.com/cilium/ebpf/cmd/bpf2go -target $GOARCH -cc clang KProbeMultiPWRU ./bpf/kprobe_pwru.c -- -DOUTPUT_SKB -DHAS_KPROBE_MULTI -I./bpf/headers -Wno-address-of-packed-member
+//go:generate go run github.com/cilium/ebpf/cmd/bpf2go -target $GOARCH -cc clang KProbePWRUWithoutOutputSKB ./bpf/kprobe_pwru.c -- -I./bpf/headers -Wno-address-of-packed-member
+//go:generate go run github.com/cilium/ebpf/cmd/bpf2go -target $GOARCH -cc clang KProbeMultiPWRUWithoutOutputSKB ./bpf/kprobe_pwru.c -- -D HAS_KPROBE_MULTI -I./bpf/headers -Wno-address-of-packed-member
+//go:generate go run ./tools/getgetter.go -struct ^(KProbePWRU|KProbeMultiPWRU|KProbePWRUWithoutOutputSKB|KProbeMultiPWRUWithoutOutputSKB)(Programs|Maps)$
+
+package main